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Issues in Aphid Biology
- Jan. 2023 [Revised]

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Polyphagy: from poly (=many [things]) phagy (=to feed on).
 
Original Greek: polyphagos meant 'excessive or abnormal eating'.
Current meaning: 'to consume many kinds of food', dates from 1770.
Not to be confused with omnivory: 'to eat every kind of food indiscriminately'.

Polyphagous aphids are unusual because most species of aphid are restricted to a single host-plant genus, and some can only raise successful colonies on one plant species (=monophagous). Whilst able to feed on many different plant species, polyphagous aphids are unable to feed on the majority.

Quantifying polyphagy

Polyphagy is not a binary all-or-nothing property, but a range - where the few aphid species which only feed on a single species of host-plant lie at one extreme. Most species of aphid are less extreme in that they have been recorded from several closely-related species, generally of the same plant genus. Somewhere in the middle of the monophagy-polyphagy range are a few species (from several Aphididae subfamilies) with 'polyphagous tendencies' - Acyrthosiphon rubi & Illinoia spiraeae (subfamily Aphidinae), Longistigma caryae, Longistigma liquidambarus, & Longistigma xizangensis (subfamily Lachninae) - plus, possibly, Pseudomegoura nipponica (Aphidinae) and several Mollitrichosiphum species (Greenideinae).

Scattered along the monophagy-polyphagy range are various aphid species which alternate between two species of plant host - the most monophagous of which alternate between just two plant species, or two plant genera (the Phylloxerid Daktulosphaira vitifoliae, alternates host-site, not host-species). Aphids that alternate their hosts are generally mono-specific or mono-generic regarding their primary host (where they may breed sexually), but are often less specific when it comes to secondary hosts (where they breed asexually). For a few asexually-reproducing 'anholocyclic' species the primary host is unknown. Not all asexual species are derived from host alternating ones. A small proportion of species (especially those alternating hosts, see below) can raise successful colonies on many distantly-related plant genera, and are considered polyphagous. Most monoecious (=non-alternating) polyphagous aphids are derived from host-alternating (=dioecious) ancestors.

Macrosiphum rosae, which mostly alternates between rosaceous plant species, has been recorded from 15 other plant families, but isn't considered especially polyphagous. Aphis gossypii, on the other hand, aside from being known from secondary hosts in more than 135 families, is also exceptional in having several unrelated primary hosts. Then again, it also has some monoecious holocyclic populations, and host-associated populations or races - at least some of which seem to function as distinct species.

Polyphagy and pest status

Not all 'pest aphids' are polyphagous (a 'pest' simply damages plants of commercial importance), but a few polyphagous aphids have become serious and cosmopolitan pests. That said, the term 'polyphagous' is not clearly defined. Some authorities treat polyphagy in terms of the number of host species, or genera, others emphasize the number of families (as we do here). That aside, the preference of a polyphagous species for each recorded host is anything but uniform, and some are only polyphagous in parts of their geographic range. Consequently their pest status varies. Some are only considered pests in the tropics, whilst some are pests of ornamentals, or in special environments such as greenhouses, warehouses or hydroponic farms.

Thus in Britain Aphis spiraecola is rare and not usually considered a pest, Aphis craccivora is a minor pest mainly found in southern Britain, and Aphis nerii is only a greenhouse pest.

Polyphagous aphids are not omniphagous. Even the most polyphagous species (in terms of families, Aphis gossypii, see graph below) is known from less than 25% of the worlds 620 plant families. Indeed, Blackman & Eastop found just 299 of those 620 families have species known to host any aphids, of which 81 host only the most polyphagous. Note, our graph only shows what Favret & Miller (2012) consider the most problematic aphid species (1.5% of more than 5200 aphid species described to date). Their 'fact sheets' include the 38 aphid species in Blackman & Eastop's dichotomous keys to polyphagous aphids, plus 28 species most frequently intercepted at United States ports of entry.

Graph data from AphID fact sheets, Favret & Miller, and Blackman & Eastop, Aphids on Worlds Plants; both accessed Sept. 2022.

Blackman & Eastop provide a key to the 35 most polyphagous aphid species worldwide: "species which occur numerous times in the host lists of many plant genera, and in some cases on plants in many different families". Their key to polyphagous aphid species that feed typically on herbs or shrubs but occasionally occur on trees, has a further 3 species (Show world list). Of those 38 aphid species, Baker (2015) lists 25 as having been recorded in Britain (Show British list).

The 'Pemphigus spp.' in Blackman & Eastop's keys are excluded, since they were evidently included because their species could not be distinguished morphologically when on secondary hosts (and most Pemphigus spp. are only known from their primary host). The most polyphagous of the Pemphigus species, Pemphigus bursarius, only host alternates between poplar and members of one family, the daisies (Asteraceae).

Polyphagy in terms of species and preference

Whilst describing the Pemphigus genus as polyphagous (because 'they all look the same to us') may be controversial, some aphid 'species' are ill-defined in practice. For instance Aphis gossypii and Aphid fabae could each be described as 'species complexes' of occasionally interbreeding host-adapted races, cryptic species, subspecies and divergent (anholocyclic) clones. Conversely, polyphagy is sometimes viewed in terms of the number of host species.

Defining 'polyphagy' whilst ignoring relative host preference is obviously misleading, albeit commonplace. For example, Blackman & Eastop (1984) considered Myzus persicae the most polyphagous aphid, albeit recorded from fewer than 1% of flowering plant species. At the same time Tuberolachnus salignus is sometimes described as polyphagous since it will utilise virtually any Salix species - there being about 350 thereof, plus hybrids. Whilst it occasionally uses Populus alba, Populus deltoides & Populus nigra, poplars are a sister genus of the same tribe (Saliceae: family Salicaceae). Only extremely rarely has Tuberolachnus salignus been recorded from hosts in another family (the Rosaceae, tribe Maleae). An unconfirmed record from Austroeupatorium inulifolium (family Asteraceae, tribe Eupatorieae) is presumably an accidental host.

When aphid populations are high a few may form colonies on less optimal, overflow hosts. We found one such colony, of Aphis fabae on cultivated rose, but even quite host-specific aphids occasionally do this. Following epidemiological reasoning, these have been described as reservoir hosts, or reserve hosts - and polyphagous species are able to use an abnormally large number thereof (Blackman & Eastop, 1984). Crops of introduced plant species could be regarded as providing a 'vacant niche' in the absence of monophagous aphid species. That said, many heavily-studied plant species have an unusually large variety of aphids recorded, including indigenous ones hosting monophagous aphids.

Thus Capsella bursa-pastoris (shepherd’s purse), a common troublesome perennial 'weed', is described by Blackman & Eastop as "a popular reserve host" throughout a large part of the world for numerous species of aphids, including many which are otherwise specific to other plant genera or families. It seems to be a plant that aphids - particularly grass and legume feeders - can utilise, and even form flourishing colonies on, usually at times of year when their normal hosts are scarce or unavailable." Capsella bursa-pastoris (family Brassicaceae) hosts 42 aphid species (plus a further 18 unconfirmed), but has two monoecious species (Dysaphis capsellae, Dysaphis rara).

Geum urbanum (herb bennet) is also sometimes seen as a reserve host: 11 species of aphid have been recorded from it, but 7 are polyphagous and two (Amphorophora gei & Macrosiphum gei) are monoecious holocyclic on Geum.

Every species of polyphagous aphid prefers some hosts to others, and are most problematic among certain plant families. In addition, aphids raised on particular hosts may become adapted to such, and develop host-specific races - as has been noted for some introduced aphids.

Host alternation and polyphagous aphids

Of the 66 species in our graphs above, 24 are known from fewer than 3 families. Defining polyphagy in terms of the number of known hostplant families does not allow us to quantitatively distinguish polyphagous aphids recorded from just one or two families from the more than 5000 non-polyphagous aphid species (host alternating species typically alternate between 2 families). We noted above that many polyphagous aphids are host-alternating, however less than 10% of all host alternating aphids are on the list below, and few of the remainder are considered polyphagous.

All of the 52 most polyphagous species listed below are Aphididae. Just two species are from subfamilies (Greenideinae, Lachninae) where alternation is unknown, the remaining 50 are from subfamilies where host alternation is common or ancestral (48 Aphidinae, 2 Eriosomatinae). Of that fifty, 22 species host alternate, 14 species do not, but the remainder cannot be classified since 13 are anholocyclic, and the life cycle of one species is unknown.

Host alternation is known from all 3 extant aphid families. Adelgids feed only on certain genera in the Pinaceae, and typically alternate between a primary Picea host and a secondary coniferous host of another genus (but the same family). Among the Phylloxeridae at least two species in subfamily Phylloxerinae alternate, between Juglandaceae and Fagaceae, but none in subfamily Phylloxerininae do. Among the Aphididae, host alternating species typically move between a woody 'primary' host or hosts (on which they can sexually reproduce) and 'secondary hosts', generally botanically-distant herbs (where they reproduce asexually, as clones). In many cases both their primary and secondary hosts are monogeneric if not monospecific, but secondary host preference tends to be less specific. Host alternation is unknown in the Chaitophorinae Chaitophorinae Drepanosiphinae, Greenideinae, and Lachninae.

Whilst a number of aphids are known to change their host preferences seasonally, among the Aphididae host alternation (in its strict form) has only been documented in four subfamilies (the Anoeciinae, Aphidinae, Eriosomatinae, and Hormaphidinae) of these the Aphidinae have the majority of species. Host alternation is widespread among the Aphidinae, which comprise roughly half of all aphid species. Of the 58% of Aphididae species that feed on non-woody hosts just 10% host-alternate, but it is assumed that non host-alternating species of Aphidinae are descendants of alternating ancestors.

Plant viruses and polyphagous aphids

An important complication in assessing crop 'risk' from polyphagous aphids arises because some can transmit plant viruses, even when the aphid-specific damage is low. The graph below shows how the number of plant viruses transmitted by each species is related to the number of families it has been recorded from.

Graph data from AphID fact sheets, Favret & Miller, and Blackman & Eastop, Aphids on Worlds Plants; both accessed Sept. 2022.

Whilst there is no obvious relationship among the less polyphagous species (recorded from <50 families), and allowing for some scatter, the more families an aphid has been recorded from the more plant viruses it is thought to carry. This relationship is not a simple linear one, which is why we have plotted the number of plant-viruses using a logarithmic (=proportional) scale. Very roughly, given an increase in 60 families the number of viruses increases ten-fold. This relationship ignores how well, or how often, each virus is transmitted. Aphis gossypii, for instance, is believed to transmit viruses rather poorly. Aphis gossypii, whilst not a forest pest, nor a temperate field-crop pest, causes serious damage to tropical crops and glasshouse plants. In other words, neither the number of host-species, host-families, nor plant-virus carried are per se indicators of pest status.

The majority of pest aphids are not especially polyphagous but, whilst confined to hosts in one family, they have more reserve hosts than their sib-species (Blackman & Eastop, 1984). Most of the cosmopolitan aphid pests are anholocyclic because conditions that trigger mating are absent, their primary host is missing, or simply because asexually reproducing populations breed faster. Cyclic parthenogenesis, by alternating a sexual generation with a number of asexual generations, readily produces clonal populations - which, although lacking sexual recombination, evolve by random mutation. Cyclical parthenogenesis is also a very successful way of exploiting the short-lived growth flushes of temperate plants. Theoretical considerations predict clonal populations often have, or evolve, a different and generally much broader host specificity than their sexually-reproducing parent population. Studies of population genetics, using DNA analysis, indicate this is true in practice.

Either way, modern farming methods, using a few genetically highly-uniform introduced intensively-cultivated varieties, provide polyphagous aphids with abundant hosts (suboptimal or otherwise) and potentially-explosive growth-opportunities.

 

The list below summarises the 52 most polyphagous species (in terms of having been recorded from more than 2 hostplant families). It comprises the 38 from Blackman & Eastop's keys, plus 14 from Favret & Miller's fact sheets, arranged in descending order of polyphagy.

1.   Aphis gossypii (Melon aphid, Cotton aphid)

Cosmopolitan. On more than 135 plant families.

The melon or cotton aphid is highly polyphagous and does not usually host alternate, reproducing all year round on its chosen host. In temperate climates it is most often seen in glasshouses on cucurbits (cucumbers and marrows) and begonias, and in gardens on ornamental Hypericum species. In East Asia, there is sometimes host alteration, with several unrelated plants being utilised as primary hosts, including: the 'Indian bean tree' (Catalpa bignonioides), Korean rose, (Hibiscus syriacus), oriental bittersweet (Celastrus orbiculatus), buckthorns (Rhamnus species) and pomegranate (Punica granatum). In the tropics Aphis gossypii is a major pest of cotton. It is distributed almost worldwide, and is particularly abundant in the tropics.

Third image above copyright Aphidnet under a Creative Commons License.

Wingless females of Aphis gossypii are usually medium-sized and blackish green or green mottled with dark green (see first picture above). In hot conditions or when crowded they are smaller and are a very pale whitish yellow. The dorsum has no dark sclerotized markings. The longest hairs on the third antennal segment are 0.3-0.5 times the basal diameter of that segment. The terminal process of the last antennal segment is 1.7-3.2 times the length of the base of that segment. The apical segment of the rostrum is 1.1 to 1.5 times the length of segment 2 of the hind tarsus. Marginal tubercles are only consistently present on abdominal tergites 1 and 7. The siphunculi are dark. The cauda is usually paler than the siphunculi and bears 4-8 hairs. The body length of adult Aphis gossypii apterae ranges from 0.9-1.8 mm.

Aphis gossypii alates (see second picture above) have 6-12 secondary rhinaria distributed on the third antennal segment and usually none on the fourth.

Read more...

2.   Myzus persicae (Peach-potato aphid)

Cosmopolitan. On nearly 130 plant families.

The peach-potato aphid does host alternate where the primary host (peach, Prunus persica) occurs. Eggs are laid on the primary host and spring colonies curl the young leaves. However, most of the population overwinters as mobile stages on herbaceous plants and brassicas. Myzus persicae is a major pest on its summer hosts including potatoes, sugar beet, lettuce, brassicas and legumes, mainly because it transmits a number of important plant viruses. Whilst Myzus persicae is a polyphagous generalist, the subspecies Myzus persicae nicotianae is a tobacco specialist.

The apterae of Myzus persicae are generally yellowish-green (see first picture above) but vary from whitish or pale yellowish green to mid-green, rose-pink or red (see second picture above). They are often darker in cold conditions. The antennae are 0.7-1.0 times the body length, reaching to the siphunculi. Their siphunculi are slightly swollen towards the darkened tips and are 1.9-2.5 times the length of the rather pointed cauda. The body length of Myzus persicae apterae is 1.2-2.3 mm.

The alate Myzus persicae (see third picture above) has a solid pigmented area occupying the mid-abdominal dorsum from segments 3 to 6, as well as further bars on adjoining segments.

Read more...

3.   Aphis fabae (Black bean aphid)

Cosmopolitan. On nearly 120 plant families.

The black bean aphid host alternates between spindle (Euonymus europaeus) as the primary host and many herbaceous plant species as secondary hosts. Sexual forms occur in autumn. Aphis fabae is found throughout the northern continents, and has been introduced to many tropical and subtropical countries where it may reproduce parthenogenetically all year round. In Europe there is a complex of sibling species or subspecies which can only be distinguished by their choice of secondary host coupled with transfer experiments.

Third image above, PaDIL. Copyright Rebecca Graham (Department of Agriculture, Western Australia)
under Commons Attribution 3.0 Australian License.

The Aphis fabae adult aptera is matt black or very dark brown, sometimes with a distinct greenish hue. It has a variable abdominal sclerotic pattern - confined to abdominal tergites 6-8 in smaller apterae, but broken bands are present in larger ones. Marginal tubercles are protuberant but small. The antennae usually have segments III-IV and the base of V quite pale. The longest femoral and tibial hairs are longer than the least width of the tibia. Their siphunculi and cauda are dark. The black bean aphid immatures (see second picture above) often have discrete white wax spots, as do sometimes the adults. The body length of Aphis fabae adult apterae is 1.2-2.9 mm.

Read more...

4.   Aphis spiraecola (Spirea aphid)

Cosmopolitan. On more than 90 plant families.

The secondary hosts of Aphis spiraecola are especially shrubs in the Caprifoliaceae, Asteraceae, Rosaceae, Rubiaceae, and Rutaceae. In North America, Brazil and Japan the species also produce sexual forms on primary host, meadowsweets (Spiraea species), or sometimes citrus or apple. Aphis spiraecola is thought to have had its origin in the Far East. In most of the rest of the world it reproduces parthenogenetically on its secondary hosts all year round. Aphis spiraecola is a major pest of citrus fruits, mountain yarrow, apple (North America) and pears (China). It has a worldwide distribution in temperate and tropical regions.

Third image above copyright Aphidnet under a Creative Commons License.

Adult apterae of Aphis spiraecola are bright greenish yellow to apple green. The abdominal dorsum is pale and usually entirely membranous. The fused last two rostral segments are less than 120 μm in length (cf. Aphis pomi which has the fused last two segments more than 130 μm in length). Marginal tubercles are restricted to abdominal tergites 1 & 7, with none present on abdominal tergites 2-4 (cf. Aphis pomi which has marginal tubercles on tergites 2-4). The femoral hairs are long and fine, the longest of them being longer than the diameter of the femur at its base. The siphunculi and cauda are black. The cauda usually has less than 12 hairs (7-15) (cf. Aphis pomi on which the cauda usually has more than 13 hairs (10-19)). The body length of an adult Aphis spiraecola aptera is 1.2-2.2 mm.

Alatae (see second picture above) have a dark brown head and thorax, and a yellowish-green abdomen with dusky marginal sclerites.

Read more...

5.   Macrosiphum euphorbiae (Potato aphid)

Cosmopolitan. On more than 90 plant families.

The potato aphid is a common and highly polyphagous species. It is often a pest on various crops such as potato (Solanum tuberosum), lettuce (Lactuca sativa) and beets (Beta vulgaris) as well as on numerous garden ornamentals. Macrosiphum euphorbiae is a vector of about one hundred plant viruses. The species originates from the north-eastern USA where it produces sexual forms and host alternates with rose (Rosa) as its primary host. Elsewhere it usually overwinters as viviparae. Aphid numbers increase rapidly from early spring, and alates spread infestations to other plants. It is an especial problem in unheated greenhouses. Macrosiphum euphorbiae was introduced to Europe about 1917 and is now cosmopolitan.

Macrosiphum euphorbiae apterae are either green with a darker green longitudinal stripe or red (see pictures above), and often rather shiny. Their eyes are noticeably red, and the antennae are darker towards their tips. The fused apical rostral segment (RIV+V) is 0.83-1.02 times longer than the second hind tarsal segment (HTII) (cf. Macrosiphum tinctum for which RIV+V is 0.98-1.11 times longer than HTII and cf. Macrosiphum funestum for which RIV+V is 1.2-1.5 times longer than HTII). Their femora are brownish and rather pale with the apices not dark or only slightly so (cf. Macrosiphum hellebori, Macrosiphum gei, Macrosiphum cholodkovskyi and Macrosiphum euphorbiellum which all have dark apices to the femora). The siphunculi are pale sometimes with the tips darker, but not as dark as the tips of the tibiae (cf. Macrosiphum rosae which has the siphunculi entirely black). The siphunculi are reticulated on the apical 13-20% and are 1.7-2.2 times the length of the cauda. The cauda is rather pointed and not constricted. The body length of Macrosiphum euphorbiae apterae is 2.0-4.0 mm.

The alate (see third picture above) has pale greenish to yellow-brown thoracic lobes, with only the antennae and siphunculi noticeably darker than in the apterae.

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6.   Aulacorthum solani (Glasshouse - potato aphid, Foxglove aphid)

Cosmopolitan. On more than 82 plant families.

In temperate climates most of the population overwinters as nymphs or wingless adults, especially on potato sprouts and on many glasshouse plants and wild species such as foxglove (Digitalis). As a result, this is often one of the first aphid species to find on young plants in the spring. The high toxicity of the saliva of the glasshouse - potato aphid may produce deformation and discoloration of leaves being fed upon. This results in direct feeding damage to potatoes and peppers. It can also be a vector of about 40 plant viruses, but its relatively poor virus transmission efficiency makes it unimportant as a virus vector in the field. Its importance is much greater in glasshouses. Its distribution is virtually cosmopolitan.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

The Aulacorthum solani apterae are pear shaped and shiny greenish yellow, usually with a bright green or rust coloured patch at the base of each siphunculus. The antennae have darkened joints and are slightly longer than the body. The siphunculi are pale with dark tips, long, slender, tapered and distinctly flanged. The body length of apterae is 1.5-3.0 mm. The winged forms have darker antennae, legs and siphunculi and have a variably developed pattern of tranverse dark bars on the dorsal abdomen.

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7.   Aphis craccivora (Cowpea aphid)

Cosmopolitan. On 80 plant families.

Aphis craccivora prefers plants in the Fabaceae (beans, peas and groundnuts), but it is highly polyphagous and has been found on many plant species. It feeds on the young shoots, leaves, flowers and fruits, and is strongly ant attended. In most places reproduction is entirely parthenogenetic with no sexual stage in the life cycle, but sexual morphs have been recorded from Germany and India. Aphis craccivora is a vector of several viruses including broad bean mosaic virus, cucumber mosaic virus and groundnut rosette virus. The cowpea aphid has a cosmopolitan distribution. It is not very common in cool temperate countries, but can be abundant in warm-temperate and tropical regions.

Third image right courtesy PaDIL, copyright Simon Hinkley & Ken Walker (Museum Victoria)
under Commons Attribution 3.0 Australian License.

The aptera of Aphis craccivora (see first picture above) is dark brown with (usually) a very solid black shiny carapace from the metanotum to abdominal tergite 6. Many North American and a few Southern European Aphis craccivora populations have a reduced sclerotic shield. The longest hair on the third antennal segment is usually 0.5-0.6 times the basal diameter of that segment (cf. Aphis pseudocomosa which has the longest hair on the third antennal segment 0.67-1.38 times the basal diameter of that segment). Their siphunculi very rarely have any trace of constriction before the flange, and are 1.2-2.2 times the length of the cauda (cf. Aphis loti which has the siphunculi 0.8-1.5 times the length of the cauda). The cauda has the distal part tapering and is 0.09-0.13 times body length (cf. Aphis loti which has the cauda finger-like, almost parallel sided on the distal part). The body length is 1.16-2.3 mm.

Aphis craccivora alatae (see second picture above) have the dorsal shield broken up into segmental bands with large marginal and postsiphuncular sclerites. Immatures are lightly dusted in wax.

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8.   Myzus ornatus (Ornate aphid, Violet aphid)

Cosmopolitan. On nearly 80 plant families.

The ornate aphid does not host alternate and is extremely polyphagous. It often occurs in mixed-species colonies, where it can be difficult to spot amongst other aphids. It is an important pest on crucifers, cucurbits and onions and also attacks peas, soybean, strawberry and many garden ornamentals, especially in glasshouses. It also feeds on some trees such as Catalpa and Prunus, often feeding away from the main veins. Sexual forms are extremely rare (oviparae are unknown and males only recorded from India) and nearly all reproduction is parthenogenetic. Not so long ago Myzus ornatus was a rare aphid. It was first discovered in England in 1932, but within a few years spread throughout the world - definitely one of Britain's more successful exports - even if its possible primary host (Spiraea lindleyana) is Himalayan.

The adult apterae of Myzus ornatus (see first picture above) are somewhat dorso-ventrally flattened. The dorsum is sclerotic and granulate, dirty yellowish to yellowish green, and is marked with conspicuous dark green or brownish transverse intersegmental sclerites. The antennal tubercles are well developed, with just a suggestion of a median frontal tubercle. The antennae are 0.5-0.6 times the body length. The siphunculi are cylindrical, slightly curved outwards, constricted below the flange and 2.1-2.7 times the length of the triangular cauda. Myzus ornatus is a very small aphid with a body length of only 1.0-1.7 mm.

The alate viviparous female (see second picture above) has a large dark dorsal patch, not touching the marginal sclerites, with some spots and cross bands on other tergites.

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9.   Neomyzus circumflexus (Crescent-marked lily aphid)

Cosmopolitan. On nearly 80 plant families.

The crescent-marked lily aphid is entirely parthenogenetic with no sexual stage in the life cycle. In temperate climates it is primarily a pest of glasshouse crops where it attacks Asparagus, Begonia, Fuchsia and many others. Heavy infestations cause direct harm to many ornamental plants, and the aphids may also transmit viruses. Neomyzus circumflexus has a cosmopolitan distribution.

Second image, copyright Nigel Gilligan, all rights reserved;
third image above by permission of Roger Blackman, copyright AWP, all rights reserved.

The apterae of Neomyzus circumflexus (previously known as Aulacorthum circumflexum) are shiny whitish, yellowish or green with black cross bands on thoracic segments, broken along the midline, and a large horseshoe-shaped spot on the back of the abdomen (see first picture above). Antennal tubercles are well developed with the inner faces parallel. The antennae are 1.1-1.5 times the body length and the antennal terminal process is approximately 5-6 times length of base of antennal segment VI. The siphunculi are dusky with a darker flange. They are rather thick and cylindrical and are 1.8-2.3 times the length of the cauda. The cauda is pale, elongate with 4-6 lateral hairs and a single dorsal preapical hair. The body length of Neomyzus circumflexus apterae is 1.2-2.6 mm.

The alate is pale green with a black head and thorax (see second picture above). The abdomen has several dark transverse bands of variable width.

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10.   Aphis (Toxoptera) aurantii (Camellia aphid, Black citrus aphid)

Cosmopolitan. On more than 70 plant families.

The black citrus aphid is found on the underside of leaves of Citrus, as well as tea (Camellia), coffee (Coffea) and mango (Mangifera). Infestation in spring can be very harmful to citrus crops. In temperate countries Aphis (Toxoptera) aurantii is a pest of ornamental Camellia bushes. Sexual forms are unknown, and aphids overwinter as viviparae. Adults stridulate by rubbing tibial spines on abdominal striae. Their distribution is now cosmopolitan.

Third image above courtesy PaDIL. Copyright Simon Hinkley & Ken Walker (Museum Victoria)
under Commons Attribution 3.0 Australian License.

Adult apterae of Aphis (Toxoptera) aurantii are oval, shiny black, brownish-black or reddish brown in colour with rather short black-and-white banded antennae. The antennal terminal process is more than 3.5 times the length of the base of the last antennal segment (cf. Aphis gossypii which has the terminal process less than 3.5 times longer than the base of the last antennal segment). The cauda and siphunculi are black, and the siphunculi are 1.0-1.5 times the length of the cauda. The cauda usually has less than 20 hairs (cf. Aphis (Toxoptera) citricidus which usually has more than 20 hairs on the cauda). A stridulatory apparatus is present below and in front of the siphunculi. The body length of Aphis (Toxoptera) aurantii apterae is about 2 mm long.

Alates (see second picture above) have the head and pterothorax blackish. The abdomen has dusky paired marginal sclerites on segments 2-5 inclusive, a pair of large postsiphuncular sclerites, and transverse dark bands across tergites VII-VIII and sometimes also on tergite VI. Their siphunculi are 1.25-1.65 times as long as the cauda.

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11.   Brachycaudus helichrysi (Leaf-curling plum aphid)

Cosmopolitan. On nearly 65 plant families.

The leaf-curling plum aphid host alternates between various plum (Prunus) species (especially domestic plum and blackthorn, Prunus spinosa) and a wide range of Asteraceae such as asters, chrysanthemums, yarrow and groundsel. Brachycaudus helichrysi populations on red clover (Trifolium pratense) have been called var warei, but are not thought sufficiently distinct to warrant subspecific status. Anholocyclic populations occur in warmer regions and in glasshouses, and are sometimes found on new growth of various trees. Brachycaudus helichrysi is a serious pest on fruit trees and sunflowers. The distribution of Brachycaudus helichrysi sensu lato is cosmopolitan, but recent molecular studies have shown they comprise at least three sibling species which evolved in geographically isolated populations.

Feeding by Brachycaudus helichrysi in spring induces pseudogall formation on their host Prunus, with the leaves rolling up tightly perpendicular to their mid-rib and laterally (see first picture above). The adult aptera of Brachycaudus helichrysi (see second picture above) is variable in colour, ranging from yellow to green to pink to white, often shiny with a slight wax dusting. Their antennae are shorter than the body with dusky tips. The dorsum of the abdomen is without a black shield. Their siphunculi are pale, tapered and short - 0.8-2.0 times the length of the cauda. The cauda is pale, short and blunt. The body length of Brachycaudus helichrysi apterae is 0.9 - 2.0mm.

The alate Brachycaudus helichrysi (see third picture above) has a dark dorsal abdominal patch, with 13-46 secondary rhinaria on the third antennal segment and 0-18 on the fourth.

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12.   Aphis nasturtii (Buckthorn - potato aphid)

Cosmopolitan. On more than 60 plant families.

The buckthorn - potato aphid host alternates between common buckthorn (Rhamnus cathartica) or alder buckthorn (Frangula alnus) as the primary host and many herbaceous plant species as secondary hosts, the most economically important of which is potato (Solanum tuberosum). Sexual forms occur in autumn. Aphis nasturtii is now of almost world-wide distribution.

The Aphis nasturtii aptera is rather bright pale green to yellowish-green in life and is not wax-powdered (see yellow aptera above in a mixed species colony of Aphis nasturtii and Aphis fabae). The abdominal dorsum is pale and membranous without dark bands or sclerites. The antenna barely exceeds half the body length. The siphunculi are usually rather pale sclerotic becoming a little darker towards the apex. The legs are dusky or rather pale - the apices of the tibiae are slightly darker as can be seen in the micrograph ventral view above. The body length of buckthorn - potato aphid apterae is 1.1-2.4 mm.

Aphis nasturtii alates (not shown) have some variably developed dorsal bands, but are always more lightly marked than Aphis frangulae alates. Immature Aphis nasturtii are green (see second picture above).

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13.   Myzus ascalonicus (Shallot aphid)

Cosmopolitan. On nearly 50 plant families.

The shallot aphid does not host alternate in the sense of regular movement from a woody (primary) host species to a herbaceous (secondary) host species. There is no sexual stage in the life cycle and no eggs are produced. Instead Myzus ascalonicus is cold-hardy, and overwinters in glasshouses and sheltered areas, especially on weeds such as chickweeds (Stellaria) and speedwells (Veronica). Numbers may build up even at low temperatures in winter and spring, with alates migrating to other hosts up to mid-June. It is extremely polyphagous, feeding on many wild plant species, as well as crops such as onions, shallots, strawberries, lettuce, brassicas and potatoes and garden ornamentals.

Myzus ascalonicus apterae are variable in colour from dark green to pale green to dirty yellow (see first two pictures above). They are noticeably shiny (cf. Myzus cymbalariae, which are not shiny). Their antennal tubercles have their inner faces approximately parallel in dorsal view (cf. Myzus cymbalariae and Myzus persicae, which have the inner faces convergent). Their legs and antennae are usually pale brown, with the ends of the antennae and the tarsi darker. The dorsum is strongly convex (see pictures above) in comparison with related species. The siphunculi are shorter than antennal segment III, distinctly swollen towards the apex, more or less evenly coloured throughout and with only a very small dusky flange (cf. Myzus persicae, which has siphunculi longer than antennal segment III and with a dark tip over the apical 5-10%). The siphunculi have their narrowest part thinner than, or equal in width to, the hind tibia at midlength (cf. Myzus cymbalariae,which has the narrowest part of the stem slightly thicker than the hind tibia at midlength). The cauda is roughly triangular in shape, and short: about one third the length of the siphunculi. The body length of Myzus ascalonicus apterae is 1.1-2.2 mm.

The alate Myzus ascalonicus (see third image above) has a large central dark patch extending over at least the central areas of abdominal tergites 3-6 or 4-6 (cf. the alate Myzus cymbalariae, which has the dorsal abdominal sclerotization at least partly divided into separate segmental cross bands).

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14.   Aphis solanella (Spindle-nightshade aphid)

Europe, Asia, Africa, South America. On more than 45 plant families.

In Europe Aphis solanella has spindle (Euonymus) as its primary host. It can also live on mock orange (Philadelphus) and viburnum (Viburnum), but it does not thrive well on the latter. Oviparae are rarely produced on Philadelphus and never on Viburnum. Aphis solanella migrates to a wide range of plants, including many used by Aphis fabae, as well as black nightshade (Solanum nigrum) and black bindweed (Fallopia convolvulus). It characteristically crumples and curls the leaves of black nightshade. Aphis solanella will not move to bean (Vicia faba), beet (Beta) or poppy (Papaver), but it can be a pest on Solanaceae, such as tomatoes (Solanum lycopersicum), potatoes (Solanum tuberosum) and peppers (Capsicum annuum), especially in warmer climates. Aphis solanella is found throughout Europe and in Asia, Africa and South America.

Adult apterae of Aphis solanella are dull black or blackish brown, occasionally with white pleural transverse wax stripes. The longest hair on antennal segment III is 0.6-1.9 times the basal diameter of antennal segment three, in most specimens shorter than 1.5 times the basal diameter. The third antennal segment of the adult Aphis solanella aptera is 11-20 times longer than the longest hair borne upon it (c.f. Aphis fabae fabae & Aphis fabae cirsiiacanthoidis where the third antennal segment is 4-9 times longer than the longest hair borne upon it). The dorsum has variable dark markings usually with dark sclerotic bands on the pronotum, mesonotum and abdominal tergites 7 and 8, and small dark marginal sclerites. They have marginal tubercles on abdominal segments VI and usually also on I (see first picture above), and sometimes smaller ones on some of the segments II-IV.

Marginal tubercles are more often present on Aphis solanella than on the different subspecies of Aphis fabae, but about 40-50% of specimens still have no marginal tubercles on II-IV. The siphunculi and cauda are dark. The body length of the adult aptera is 1.2-2.6 mm.

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15.   Aphis odinae (Mango aphid)

Southern, South-east and East Asia, Africa, Southern Europe. On more than 45 plant families.

Aphis odinae is found on numerous shrubs and trees in east and south-east Asia, mostly in the plant families Anacardiaceae (e.g. Mangifera, Rhus), Araliaceae (e.g. Aralia), Caprifoliaceae (Viburnum), Ericaceae (Rhododendron), Pittosporaceae (Pittosporum), Rubiaceae (e.g. Coffea), and Rutaceae (Citrus). They feed on undersides of leaves of host plants along main veins (see picture above) and in dense colonies on young shoots, and are attended by ants. Over most of its distribution Aphis odinae is anholocyclic, but in Japan there is at least a partial sexual phase, with sexuales produced in autumn on various plants, and fundatrices found in spring. The mango aphid is found over most of Southern and South-East Asia, China, Korea and Japan, as well as in Africa south of the Sahara, Greece and Hawaii.

First image above by permission, copyright Lu Zhaozhi, all rights reserved.
Second image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka (accessed 12/2/20).
Third image above copyright Brendan Wray under a Creative Commons Attribution-Noncommercial 3.0 License.

Adult apterae of Aphis odinae are usually grey-brown to reddish-brown (see first picture above) but, in east Asia, a dark green form also occurs. Both their siphunculi and cauda are dark. The antennal terminal process is 2.5-3.0 times as long as the base of antennal segment VI (cf. Aphis aurantii and Aphis citricidus, which have the terminal process 3.5-5.0 times as long as the base of antennal segment VI). A stridulatory apparatus is present, comprising a pattern of ridges on the ventro-lateral areas of abdominal sternites V and VI, and a row of short, peg-like hairs on the hind tibia. The siphunculi are only 0.4-0.6 times as long as the cauda (cf. Aphis aurantii which has the siphunculi 0.9 - 1.5 times as long as the cauda). The body length of adult Aphis odinae apterae is 1.3-2.4 mm.

Alate Aphis odinae (see second picture above) are similarly-coloured to the adult apterae (red-brown or dark green) with dark siphunculi.

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16.   Rhopalosiphum nymphaeae (Water lily aphid)

Cosmopolitan. On more than 45 plant families.

In spring the water lily aphid feeds on various Prunus species (such as Prunus spinosa) where it feeds on leaf petioles and fruit stalks curling the leaves. In early summer Rhopalosiphum nymphaeae winged adults migrate to the secondary hosts comprising a large variety of water plants, including Nymphaea (water lilies), Potamogeton (pondweeds), and Sparganium (arrowheads). Its distribution is almost cosmopolitan - in Britain it is found from the south of England to the north of Scotland.

Third image above courtesy PaDIL. Copyright Simon Hinkley & Ken Walker (Museum Victoria)
under Commons Attribution 3.0 Australian License.

Apterae of Rhopalosiphum nymphaeae are brownish on the primary host (plum), and more or less shiny reddish-brown to dark olive (see first picture above) on the secondary host (water lily). The dorsal cuticle has reticulation formed by regularly shaped roundish bead-like spinules. The antennae are about 0.6 times the body length. The terminal process of antennal segment VI is about 3-4 times the length of the base of that segment. On the primary host the apical rostral segment (RIV+V) is 1.0-1.1 times longer than the second hind tarsal segment (HTII). On the secondary host RIV+V is 1.15-1.45 times longer than HTII. The siphunculi are more than twice the length of the cauda and are swollen on the distal half. The cauda is elongate and slender. The body length of Rhopalosiphum nymphaeae aptera is 1.6-2.6 mm.

Rhopalosiphum nymphaeae alatae (see second picture above) are shining brown, sometimes with white dorsal wax markings. The immatures (and sometimes the adults) may be dusted with a light grey wax on the head, thorax and legs.

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17.   Pseudomegoura magnoliae (Oriental magnolia aphid)

South & East Asia. On nearly 45 plant families

Pseudomegoura magnoliae feeds on the stems and leaves of plants in many different families, including important crops (Citrus, Malus, Brassica, Solanum, Vicia, various Cucurbitaceae), and many ornamental shrubs and trees. It has one of the broadest host preferences of any aphid found in the Indo-Asian region. Direct feeding damage is common, but the species is not thought to be involved in virus transmission. Pseudomegoura magnoliae is mainly anholocyclic. Males and (a very few) oviparous females have been recorded in Japan and India, but sexual reproduction seems to be very rare. Pseudomegoura magnoliae is found in Japan, China, Korea and India.

Both images above copyright Aphidnet under a Creative Commons License.

Adult apterae of Pseudomegoura magnoliae have the front of the head and the prothorax reddish. The rest of the body varies from green to yellow-green to bright orange, with mostly black femora, and the tibiae and antennae usually wholly black. The siphunculi are pale basally and dark distally, and the cauda is dark. The body length of adult apterae is 2.3-3.9 mm.

18.   Smynthurodes betae (Bean root aphid)

Cosmopolitan. On more than 35 plant families

Where the primary host (Pistacia) is found, the bean root aphid goes through its full life cycle, host alternating from Pistacia to numerous secondary hosts, especially in the Asteraceae, Fabaceae and Solenaceae. It lives on the roots of the secondary hosts, where it can be a major pest. Smynthurodes betae can also persist on its secondary hosts as anholocyclic parthenogenetic populations. It commonly overwinters in ant's nests. Anholocyclic parthenogenetic populations of Smynthurodes betae are found in most countries of the world, except the coldest parts. It goes through its full life cycle in North Africa, Israel, Syria, Iran, southern Crimea, Transcaucasus and Pakistan.

Third picture above courtesy Favret, C. & G.L. Miller, AphID.
Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

On the primary host (Pistacia), Smynthurodes betae fundatrices induce small red midrib galls, and their offspring induce yellow-green or red spindle-shaped leaf margin galls. On the secondary host (roots of many plants) adult apterae are small to medium-sized, globular in shape, and coloured a dirty yellowish white (see first picture below). They are wax dusted, and clothed with numerous fine hairs. Their immatures are light green (see second picture above). The head, prothorax, antennae and legs are light brown. The antenna are 5-segmented (cf. Trama species which have six antennal segments) and the second antennal segment is elongated and about the same thickness as the third antennal segment. There are thick sclerotized rims on the primary rhinaria of the last two antennal segments. There are no siphunculi (cf. Protrama, Tetraneura and Anoecia species, which have siphunculi). The body length of the adult Smynthurodes betae aptera is 1.6-2.7 mm.

Alates of Smynthurodes betae have dark transverse bars on the abdominal tergites.

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19.   Sinomegoura citricola (Wine-red citrus aphid)

East, South & South-east Asia, Australia, USA. On nearly plant 35 families.

Sinomegoura citricola feeds on the undersides of leaves or young growth of numerous tropical shrubs and some trees, especially Lauraceae and Rutaceae. It is particularly important on citrus, avocado, fig, mango, and tea, but has not been implicated in the transmission of any plant virus. It appears to be mainly or entirely anholocyclic, as no sexuales have ever been found. It is found throughout India, Sri Lanka, China, Thailand, Korea, Taiwan, Japan, Malaysia, Indonesia, and the Philippines, and is invasive in Australia and California.

Both images above copyright Aphidnet under a Creative Commons License.

Adult apterae of Sinomegoura citricola are spindle-shaped, coloured shiny dark brown to reddish-brown with bright red eyes. The siphunculi are pale at their bases and dark on about the distal two-thirds, and have no polygonal reticulation. The siphunculi are 0.75-1.0 times the length of the long, dark, pointed cauda. The cauda bears 10-24 hairs. The body length of adult apterae is 1.4-2.7 mm.

20.   Aphis citricidus (Brown citrus aphid)

Cosmopolitan in subtropical and warm temperate countries. On nearly 30 plant families.

Aphis citricidus is mainly found on young growth of plants in the citrus family (Rutaceae), although large colonies of aphids occasionally develop on young growth of other trees and shrubs. Citrus is undoubtedly the main host, where the aphid rolls the leaves and stunts shoots sometimes causing significant damage. However, most damage results from transmission of the tristeza virus. Aphis citricidus colonies are ant-attended. The species is anholocyclic in most parts of the world - but a sexual phase has been recorded on Citrus unshiu in Japan, suggesting that is where the species originated. The brown citrus aphid is found in southern Africa, southern Asia, Australia, New Zealand, Pacific islands and subtropical and warm temperate parts of South America. More recently it has spread to important citrus-growing areas in Central America, the Caribbean and southern USA, as well as to Madeira, Portugal and north-western Spain. It has not so far reached the Mediterranean region nor the Middle East.

First image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka. (accessed 12/8/20).
Second image copyright Marco Gaiani; third image copyright Brendan Wray,
both under a Creative Commons License.

Adult apterae of Aphis citricidus (previously Toxoptera citricida) are shiny, very dark brown to black, with dark siphunculi and cauda (see first picture above) (cf. Aphis spiraecola, which are yellow or green). The antennae of adult wingless forms and larger nymphs are not striped, but are dark on about the distal half of its length (cf. Aphis aurantii, which has black-and-white banded antennae; and cf. Aphis craccivora, which has the antenna dark on only the distal 0.3 of its length). The terminal process is 4.0-4.5 times as long as the base of antennal segment VI. The longest hairs on antennal segment III are 1.5-2.0 times the basal diameter of that segment (cf. Aphis aurantii, which has the longest hairs on that segment 0.5-1.0 times the basal diameter). The siphunculi are about 1.5 times as long as the cauda. The body length of adult Aphis citricidus apterae is 1.5-2.4 mm.

Alatae of Aphis citricidus have a shiny black abdomen. Antennal segment III is dark (cf. Aphis aurantii, which has antennal segment III mainly pale). The forewing has a pale pterostigma and a twice-branched medial vein (cf. Aphis aurantii, which has a very dark pterostigma, and usually a once-branched media). Immature Aphis citricidus are a distinctive orange-brown (see second picture above).

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21.   Acyrthosiphon malvae (Geranium aphid, Pelargonium aphid).

Cosmopolitan. On more than 25 plant families.

Acyrthosiphon malvae is found on many plants, but particularly herbaceous Rosaceae. It is a pest of ornamentals, rather than of crops. There are many subspecies, mostly with specific host-plant associations. Acyrthosiphon malvae sstr. are pale green or red aphids on many Geraniaceae and Malvaceae worldwide, as well as plants in other families. Acyrthosiphon malvae ssp. agrimoniae is yellowish green and found in flowerheads or on undersides of leaves of Agrimonia species (agrimony) in Europe and western Asia. Acyrthosiphon malvae ssp. poterii is bright salmon pink, yellowish or green and found on Poterium sanguisorba (= Sanguisorba minor) (salad burnet), and is only known from England. Acyrthosiphon malvae ssp. potha is pale yellowish or greyish green and associated with Alchemilla species (lady's mantle) throughout Europe. Acyrthosiphon malvae subspecies rogersii (Theobald) is green or yellow-green, often shiny, and may form large colonies on young leaves of Fragaria (strawberry) in north and west Europe. The geranium aphid does not host alternate. All subspecies spend their entire life cycles on their respective host plants, overwintering in the egg stage. Distribution varies according to subspecies (see above).

Acyrthosiphon malvae apterae are green, yellowish or greyish green, or pinkish red (see first two pictures above). The femora and siphunculi are pale. The terminal process of antennal segment VI is 4.8-5.8 times the length of its base. The longest hair on antennal segment III is 0.7-1.0 times the diameter of that segment and the apterae have 1-24 secondary rhinaria on that segment. The fused apical rostral segments are 1.1-1.4 times the second hind tarsal segment. Their siphunculi have no polygonal reticulation, are cylindrical on the distal half and are 1.8-2.2 times the pale caudal length. The body length is 1.5-3.2 mm.

The alate Acyrthosiphon malvae (shown giving birth in third picture above) has antennae longer than the body with 12-31 secondary rhinaria on antennal segment III. The abdomen is usually unsclerotized but may have small spinal and intersegmental pleural sclerites. The siphunculi and cauda are more slender than in the apterae.

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22.   Rhopalosiphoninus latysiphon (Bulb-and-potato Aphid)

Cosmopolitan except in polar regions. On more than 25 plant families.

Rhopalosiphoninus latysiphon feeds on bulbs, especially tulips (Tulipa) and Gladiolus, potato (Solanum tuberosum) tubers in store, and on roots of many plants including potatoes and various ornamentals, or on etiolated runners growing in darkness under stones, as in sterile bromegrass (Bromus sterilis) & field bindweed (Convolvulus arvensis). It has been implicated in the transmission of at least 4 plant viruses. Populations are anholocyclic, and no sexual morphs have been observed. Rhopalosiphoninus latysiphon is found in Europe, Asia, Middle East, Australasia, North and South America, and parts of Africa (Rwanda, Kenya, South Africa).

First image above, copyright Ad Sonnemans, Second image copyright Aphidnet;
both under a public domain (CC0) licence.

Adult apterae of Rhopalosiphoninus latysiphon are shiny dark olive green with very strongly swollen shiny black siphunculi. The swollen part of the siphunculi is 3.7-4.8 times thicker than the narrowest part of the stem (cf. Rhopalosiphoninus staphyleae which has mainly pale siphunculi with the swollen part no more than 3.2 times thicker than the narrowest part). The body length of adult apterae is 1.4-2.5 mm. Alatae have shiny olive-green to black dorsal abdominal markings.

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23.   Rhopalosiphum rufiabdominale (Rice root aphid)

Cosmopolitan in warmer climates. On more than 22 plant families.

Rhopalosiphum rufiabdominale is native to east Asia where it host alternates from Prunus species, including Japanese apricot (Prunus mume) and Chinese plum (Prunus salicina), to the roots of various grasses (Poaceae), sedges (Cyperaceae), potatoes / nightshades (Solanaceae), and cannabis (Cannabaceae). It has also been found overwintering in Europe on domestic plum (Prunus domestica) and apricot (Prunus armeniaca). Rhopalosiphum rufiabdominale is found in warmer climates, or glasshouses, in much of the rest of the world as anholocyclic populations on the secondary hosts. It is a major pest of rice in east Asia and of cannabis in hydroponic cultivation.

First image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka (accessed 12/2/20).
Second image above copyright Whitney Cranshaw & third image copyright Brendan Wray, AphID, USDA APHIS PPQ, Bugwood.org; both under a Creative Commons License.

Adult apterae of Rhopalosiphum rufiabdominale on the primary host (not pictured) are reddish-brown or greenish-brown with bluish-white mealy wax on the sides of the body and forming dorsal cross-bands. Apterae on the secondary host are dark green or brownish with a rusty-red suffusion about the bases of the siphunculi (see pictures above - note they are of immatures). The hairs on antennal segment III are markedly longer than the basal diameter of that segment; on the secondary host the longest hairs are 3-5 times the basal diameter (cf. Rhopalosiphum nymphaeae and Rhopalosiphum padi, which has the hairs on antennal segment III shorter than or equal to the basal diameter of that segment). Marginal tubercles are usually only present on abdominal tergites I and VII (cf. Rhopalosiphum nymphaeae, which has marginal tubercles on tergites I-VII). The siphunculi are less than 0.3 mm long, or 1.7-1.8 times longer than the cauda, and with no discernible subapical swelling (cf. Rhopalosiphum nymphaeae, which has siphunculi more than 0.3 mm long and swollen proximal to the subapical constriction). The body length of adult Rhopalosiphum rufiabdominale apterae is 2.0-2.6 mm.

Alatae on the secondary host are dark green with a rusty suffusion around the bases of the siphunculi. They usually have 5-segmented antennae with 3-35 secondary rhinaria on antennal segment III, and 0-4 on segment IV.

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24.   Rhopalosiphum padi (Bird cherry - oat aphid)

Cosmopolitan. On more than 20 plant families.

The bird cherry - oat aphid host alternates between bird cherry (Prunus padus) as the primary host and various grasses (Poaceae) as the secondary host. Some populations reproduce parthenogenetically all year on grasses. Rhopalosiphum padi is the principal vector of barley yellow dwarf virus, and has a cosmopolitan distribution.

On the primary host (bird cherry) feeding by the fundatrix of Rhopalosiphum padi & her offspring induces a rolled leaf gall (see first picture above). Apterae in the gall have a coating of mealy wax (see second picture above). Apterae on the secondary host (grasses) (see third picture above) are pale green to dark green, brown or nearly black, with a rust-red suffusion around the base of each siphunculus. The terminal process of the sixth antennal segment of the aptera is 3.1-5.2 times as long as the base of that segment. The apical ends of the siphunculi are slightly swollen and end with a strong flange preceded by a distinct constriction. The cauda is rather pale and shorter than the siphunculi. The body length of Rhopalosiphum padi apterae is 1.2-2.4 mm.

The alate vivipara of Rhopalosiphum padi is green, with a rusty red suffusion around the siphuncular bases. It has marginal tubercles on most or all of abdominal segments I to VII. The apical rostral segment (RIV+V) is 0.75-0.95 times as long as the second hind tarsal segment (HTII). The longest hairs on antennal segment III are 0.53-0.76 times the basal diameter of that segment.

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25.   Myzus cymbalariae (Cymbalaria aphid)

Cosmopolitan. On more than 20 plant families.

The cymbalaria aphid does not host alternate, but is extremely polyphagous, feeding on a similar range of hosts to Myzus ascalonicus including Alliaceae, Caryophyllaceae, Scrophulariaceae, and Violaceae. There is no sexual stage in the life cycle and no eggs are produced. Like Myzus ascalonicus, Myzus cymbalariae was first found in Britain (in 1954), and has since spread to many parts of the world.

Third image above, by permission of Roger Blackman, copyright AWP all rights reserved.

Adult apterae of Myzus cymbalariae (see first picture above) are matt yellowish green or yellowish brown to dark brown or deep crimson red (cf. Myzus ascalonicus which are shiny). The antennal tubercles have their inner faces apically convergent in dorsal view (cf. Myzus ascalonicus which has the inner faces approximately parallel in dorsal view). Their legs and antennae are pale, apart from the ends of the antennae and the tarsi. The dorsal cuticle is scaly (cf. Myzus ascalonicus which does not have the dorsal cuticle scaly). The siphunculi are shorter than antennal segment III, distinctly swollen towards the apex, evenly coloured throughout and with only a very small flange. The narrowest part of the stem of the siphunculi is slightly thicker than the hind tibia at midlength (cf. Myzus ascalonicus which has the narrowest part of the siphunculi equal in width or thinner than the hind tibia at midlength). The cauda is roughly triangular in shape, and short: about one third the length of the siphunculi. The body length of Myzus cymbalariae apterae is 1.2-2.0 mm.

The alate Myzus cymbalariae (see second picture above) has the dorsal abdominal sclerotization at least partly divided into separate segmental cross bands (cf. the alate Myzus ascalonicus which has a large central dark patch extending over at least the central areas of abdominal tergites 3-6 or 4-6).

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26.   Sitobion avenae (English grain aphid)

Europe, North Africa, Middle East, Asia. On nearly 20 plant families.

There is no host alternation, and the species spends its entire year on cereals and grasses. It occurs on all cereals including rice and maize and can develop on most grasses (Poaceae), as well as on some rushes (Juncaceae) and sedges (Cyperaceae). The majority of the population is anholocyclic (produces only asexual morphs) and overwinters as nymphs or apterae on grasses or winter cereals, but a small proportion of the population is holocyclic (=alternates parthenogenetic with sexual reproduction) and overwinters as eggs which hatch in March. Sitobion avenae is widespread throughout the world, with a preference for temperate climates. It occurs widely in Europe, North Africa, the Middle East and Asia.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

The adult aptera of Sitobion avenae (see first picture above) is medium-sized and spindle-shaped. It shows colour polymorphism with green and brown forms predominating (immatures are green or red.) The antennae are black and somewhat shorter than the body. The legs are yellow but with the tips of femora, tarsi and tibiae dark. The siphunculi are cylindrical and black and somewhat longer (1.1-1.5 ×) than the pale pointed cauda (cf. Sitobion fragariae which also occurs on grasses, but has its siphunculi 1.7-2.7 × the length of the more rounded cauda). The body length of the aptera is 1.3-3.3 mm. long.

The alate (see second picture above) is 1.6-2.9 mm. long and also occurs in two colour forms - green and brown. It has distinct dark intersegmental markings on the upper surface of the abdomen.

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27.   Aphis nerii (Oleander aphid)

Cosmopolitan. On 18 plant families.

Aphis nerii is a specialized feeder on oleander (Nerium oleander), but may occur on other Apocynaceae species - especially Dregea sinensis and milkweeds (Asclepidaceae) where it forms large colonies on growing shoots and along midribs of leaves. Among other host families, it has been reported feeding on Asteraceae, Convolvulaceae and Euphorbiaceae - albeit sometimes as overflow hosts. It is anholocyclic virtually everywhere except, perhaps, Japan. Aphis nerii is distributed more or less worldwide in warmer climates. It is also found in protected environments (glasshouses) in temperate countries, and occasionally 'in the field'.

First two images above copyright Alan Outen, all rights reserved;
Third image courtesy Favret, C. & G.L. Miller,AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

Adult and immature apterae of Aphis nerii are bright yellow-orange or lemon-yellow, with dark antennae. The antennal terminal process is 3.4-4.7 times the length of the base of the sixth antennal segment. The abdominal dorsum is entirely membranous. The legs including the hind tibiae are dark (cf. Aphis asclepiadis and several polyphagous Aphis species which have the hind tibiae pale for more than half their length). The rather long siphunculi and finger-shaped cauda are black, and the siphunculi are 1.7 - 2.7 times as long as the cauda. The body length of adult Aphis nerii apterae is 1.3-1.7 mm. The pictures above show live immatures on one of their preferred hosts, milkweed (an Asclepias species).

Aphis nerii alatae (see second picture above) have large black postsiphuncular sclerites and smaller, often pale and inconspicuous marginal sclerites, but no mid-dorsal bands.

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28.   Aphis sambuci (Elder aphid)

Europe, North Asia, North America (recorded from 17 plant families)

The elder aphid normally host alternates between elder (Sambucus nigra) in spring, where it forms dense colonies, and the roots and root collars of various herbs such as docks (Rumex) and campions (Silene). Sexual forms of Aphis sambuci occur in autumn. It is strongly ant attended on the primary host and sheltered by ants on the secondary host roots. It occurs throughout the northern continents.

Third image above courtesy Favret, C. & G.L. Miller, AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO.

On their primary host (elder), Aphis sambuci apterae (see first picture above) are very variable in colour from dark green through to yellowish brown; on their secondary host (e.g. root collar of dock) Aphis sambuci are usually dark green. Adults and immatures often have white waxy stripes across the sides of the abdominal segments. Antennae, siphunculi and legs blackish on the primary host and brownish in root colonies. The dorsal abdominal sclerotic pattern comprises small marginal and postsiphuncular sclerites, dark intersegmental muscle sclerites and variably complete transverse bands across tergites 6-8. Tergites 1-4 and 7 have marginal tubercles (visible if you expand the images above) between their dark marginal sclerites. The cauda is dark and bluntly tapering. The body length of adult Aphis sambuci apterae is 2.0-3.5 mm.

Alates (see second picture above) have larger postsiphunculars, well developed marginals, stronger bands on tergites 7-8 and some unpaired median dorsal sclerites.

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29.   Longistigma caryae (Giant bark aphid)

North America. On more than 16 plant families.

Longistigma caryae do not host alternate, but are highly polyphagous, being found on the bark of numerous tree species in North America including basswood (Tilia spp.), hickories & pecan (Carya spp.), oaks (Quercus spp.) and sycamores (Platanus spp.). In northern USA and Canada sexual forms develop in autumn, producing alate males and apterous oviparae. The population then overwinters in the egg stage. In southern states of the USA populations are anholocyclic.

First image above by permission, copyright Claude Pilon, all rights reserved.
Second image above copyright Katja Schulz under a Creative Commons Attribution 2.0 Generic license. Third image copyright Brendan Wray, AphID, USDA APHIS PPQ, Bugwood.org under a Creative Commons Attribution-Noncommercial 3.0 License.

Adult apterae of Longistigma caryae are pale brownish-grey with 2 longitudinal rows of large black spots (not sclerotised) on each side of the median line of the dorsum, and a transverse series of small black spots along the intersegmental lines. Their dorsum is covered with a variable amount of bluish-white wax powder, and the body, legs and antennae have conspicuously long brown hairs. Antennal segment III is equal in length to segments IV plus V, whilst segment VI is short, about 3 times longer than wide and with the terminal process thumb-shaped. The coxae are dusky, the trochanters and femora, except tips, are reddish-brown, and the tips of the femora, together with tibiae and tarsi, are black except that the middle of the tibia is sometimes reddish-brown. The second hind tarsal segment (HTII) is 1.8-2.3 times the length of the first hind tarsal segment (HTI). The truncate siphuncular cones are black and hairy. The body length of adult Longistigma caryae apterae is 5.1-7.8 mm.

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30.   Rhopalosiphoninus staphyleae (Mangold aphid)

Europe, South & East Africa, North America, Australasia. On more than 16 plant families.

The primary host of Rhopalosiphoninus staphyleae s. str. is bladdernuts (Staphylea spp.). Feeding by the aphid causes the leaves to curl and become mottled pale yellow. This aphid can be holocyclic in Europe, host alternating from late May onwards to its secondary hosts in the Liliaceae and Iridaceae (Tulipa, Hemerocallis, Crocus, Anthericum), and sometimes to the roots of plants (herbs, trees, grasses) in several other families. However, anholocyclic populations on the secondary hosts are also common, being found in Europe and North America, as well as Kenya, South Africa, Australia and New Zealand. The subspecies known as Rhopalosiphoninus staphyleae tulipaellus is found in Europe (and possibly America). Rhopalosiphoninus staphyleae tulipaellus is entirely anholocyclic on roots, especially on beets in store, giving it the common name of mangold aphid. Its status is unclear, but some authorities consider it a good (=genuine) species.

First two images above copyright Zoran Gavrilovic, all rights reserved;
third image copyright Brendan Wray, AphID, USDA APHIS PPQ, Bugwood.org under a Creative Commons License.

Adult apterae of Rhopalosiphoninus staphyleae on their primary host (Staphylea) are pear shaped, yellowish-white or pale yellow, with a translucent whitish spot on the anterior part of the dorsal abdomen (see pictures above). Apterae on the secondary host, and also in populations remaining through summer on the primary host (not pictured), are dark olive green or brownish with very dark green or black dorsal markings. The antennae are about the same length as, or slightly shorter than, the body, mostly pale, but with the apex of segment V and the whole of segment VI dark; the terminal process is 3.75-4.55 times as long as the base of antennal segment VI. Antennal segment III has 1-7 secondary rhinaria (cf. Rhopalosiphoninus latysiphon, where segment III has none). Antennal hairs are very short. The siphunculi are swollen, very pale with only the tip dusky or dark, and with a well developed flange. The swollen part is no more than 3.2 times thicker than the narrowest part of the stem (cf. Rhopalosiphoninus latysiphon, which has the swollen part 3.7-4.8 times thicker than the narrowest part). The siphunculi are 2.5-3.0 times the length of the cauda - which is pale, triangular with a very blunt apex and usually bearing 5 hairs. The body length of adult Rhopalosiphoninus staphyleae apterae is usually given as 1.5-2.3 mm (but in Aphids on Worlds Plants it is 2.3-3.0 mm).

Rhopalosiphoninus staphyleae alatae (not pictured live, but see clarified mount second picture below) have an olive-green abdomen with an extensive dark green to black sclerotic dorsal patch.

There are two subspecies. Rhopalosiphoninus staphyleae s. str. has variably developed dusky to dark, often fragmented crossbands in the summer form of the aptera, and antennal segment III usually has 1-2 secondary rhinaria. Rhopalosiphoninus staphyleae ssp. tulipaellus usually has a dark sclerotic trapezoid central patch on abdominal tergites III-V or IV-V, and antennal segment III usually has 2-4 secondary rhinaria.

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31.   Macrosiphum rosae (Rose aphid)

Cosmopolitan. On 16 plant families.

The rose aphid usually overwinters in the egg stage on rose bushes (its primary host), although in mild winters some adults may continue to reproduce parthenogenetically. In spring they colonise the young growth of rose, and produce large numbers of alates. These mostly migrate to their secondary hosts, teasels (Dipsaceae) and valerians (Valerianaceae). However, colonies can be found all summer on rose and the species is an important horticultural pest. Macrosiphum rosae has a worldwide distribution.

Adult Macrosiphum rosae apterae are green or deep pink to red-brown. The antennae and sometimes the head are dark, as are the ends of the tibiae and femora. The abdomen may or may not have small marginal sclerites and antesiphuncular sclerites. The siphunculi are black and bent outwards and are reticulated on the apical 10-17%. They are about 0.27-0.41 times the body length and 1.9-2.4 times the length of the cauda. The cauda is pale yellow. The adult aptera of Macrosiphum rosae is 1.7-3.6 mm long.

Macrosiphum rosae alatae have conspicuous black sclerites along the sides of the abdomen (see third picture above). They also have green and red colour forms. Immatures are similar in appearance to the adult apterae, but the cauda is not developed and the siphunculi are dusky, not black.

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32.   Abstrusomyzus phloxae (Obscure dark-tipped aphid)

North America. On more than 15 plant families.

Abstrusomyzus phloxae is a polyphagous species, having been recorded from several Asteraceae (Achillea, Agoseris, Centaurea) and from a number of unrelated genera including Apocynum, Capsella, Carex, Cerastium, Galium, Phacelia, Phlox, Plantago, Polygonum, Ranunculus, Stellaria, Trifolium, Viola. In the eastern USA Abstrusomyzus phloxae is most common on Plantago, and in the western USA it is common on Apocynum. Note that Abstrusomyzus on strawberries (Fragaria spp.) are more likely to be Abstrusomyzus valuliae and on Oxalis spp. are more likely to be Abstrusomyzus reticulatus (Jensen & Stoetzel, 1999). Usually Abstrusomyzus phloxae colonizes the basal or rosette leaves of low-growing plants where colonies are often ant-tented. On Apocynum it feeds on the undersides of leaves causing characteristic leaf tissue yellowing. Abstrusomyzus phloxae mainly reproduces parthenogenetically all year, but oviparae have been found in Nova Scotia. The species is widely distributed in North America.

First image above copyright Andrew Jensen under a cc by-nc-sa licence
Second image above copyright Gregory Parks, AphID, Bugwood.org under a cc by-nc-sa licence.

Adult apterae of Abstrusomyzus phloxae are pale apple-green with faint orange patches around their siphuncular bases. The head is ornamented with numerous spicules, and the antennal tubercles are moderately developed with prominent converging scabrous processes extending from the antennal bases. The dorsal abdomen is without dark markings, but does have hexagonal reticulation which is faint due to the pale, unsclerotized tergum (cf. Abstrusomyzus reticulatus, Abstrusomyzus valuliae & Abstrusomyzus leucocrini, which all have the dorsum of the abdomen dark pigmented, usually black). The siphunculi are mostly pale but with a dark tip (cf. Aphis asclepiadis, Aphis fabae, Aphis gossypii, Aphis plantaginis, Aphis frangulae, Aphis spiraecola & Protaphis middletonii, all of which have dark siphunculi). The siphunculi are slightly swollen subapically over about the distal quarter (cf. Aulacorthum solani, Myzus ornatus & Neomyzus circumflexus, which have the distal half of the siphunculi tapering or cylindrical, and Rhopalosiphoninus latysiphon and Rhopalosiphoninus staphyleae, which have the siphunculi markedly swollen). The body length of adult Abstrusomyzus phloxae apterae is 1.2-1.8 mm.

The dorsal abdomen of the alate Abstrusomyzus phloxae (see second picture above) has dark lateral sclerites, with interrupted cross bands on some segments which often have hexagonal reticulation similar to the tergum of apterous vivipara.

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33.   Acyrthosiphon pisum (Pea aphid)

Cosmopolitan. On 13 plant families.

The pea aphid can be found feeding on about 20 genera in the family Fabaceae but especially on Medicago, Melilotus, Trifolium, Dorycnium and Lotus. Acyrthosiphon pisum is a major pest of peas and alfalfa, partly because of direct feeding damage and partly because of virus transmission. Adults readily fall to the ground if the plant is disturbed. The pea aphid is found worldwide in temperate climates.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

Acyrthosiphon pisum apterae (see first picture above) are pale green or pink with red eyes. The antennae of Acyrthosiphon pisum are 1.0-1.6 times as long as the body. The antennal segments, tibiae and siphunculi have dark apices (cf. Acyrthosiphon loti which does not have the antennal joints darkened). The siphunculi are tapering and very thin with the diameter of a siphunculus in the middle less than the diameter of the hind tibia; the siphunculi are 1.2-1.9 times the length of the cauda. The cauda is long and tapered. The body length of Acyrthosiphon pisum apterae ranges from 2.2 to 5.0 mm long.

The alate viviparous female (see second picture above) has the head and thorax only slightly darker than the abdomen which is pale with small marginal sclerites.

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34.   Myzus antirrhinii (Snapdragon aphid)

Europe, East Asia, Australia and western North America. On 13 plant families.

Myzus antirrhinii feeds on the leaves and young growth of numerous plants, especially perennials, on which it may be confused with Myzus persicae. Unlike the latter, it forms large dense colonies, but so far has not been implicated in the transmission of any plant virus. It is especially known to feed on ornamentals such as Japanese mock orange and Japanese cheesewood (Pittosporum), and sweetshade (Hymenosporum). It has not been implicated in the transmission of any plant virus. Unlike Myzus persicae, Myzus antirrhinii often forms large, dense colonies, and only produces alatae rather sporadically. Populations are anholocyclic almost everywhere, and are most often found on perennial plants. However, there is now evidence of a possible sexual phase in Japan. Myzus antirrhinii is found throughout Europe, east Asia, Australia and western North America.

Images above by permission of Roger Blackman, copyright AWP all rights reserved.

Apterae of Myzus antirrhinii are mid grey-green to dark green, occasionally dark red; they are very similar in appearance to Myzus persicae. The apical rostral segment (RIV+V) is 0.102-0.128 mm in length (cf. Myzus persicae which is 0.090-0.122 mm. in length). The siphunculi are uniformly darker and more swollen distally than is the case with Myzus persicae. The body length of adult apterae is 1.4-2.2 mm.

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35.   Nasonovia ribisnigri (Currant-lettuce aphid)

Europe, West & Central Asia, North & South America. On 13 plant families.

The currant-lettuce aphid host alternates from currants (Ribes spp.), especially gooseberry and blackcurrant, to various Asteraceae, including lettuce, as well as Brassicaceae, Scrophulariaceae and Solanaceae. Nasonovia ribisnigri is found throughout Britain and continental Europe east to Ukraine, and has been introduced to North and South America.

Nasonovia ribisnigri apterae on the primary host (gooseberry and blackcurrant, see first picture below) are shiny green with no dark markings. On their secondary host (various members of the daisy family) Nasonovia ribisnigri apterae are more variable in colour, ranging from green to yellow or pink, and have dark intersegmental sclerites between each abdominal segment (see second picture above). The length of the terminal process is 7.0-11.4 times the length of the base of the antennal segment VI (cf. Nasonovia pilosellae which has the length of the terminal process 3.4-8.3 times longer than the base). The first segment of the hind tarsus has three hairs. Nasonovia ribisnigri siphunculi are pale with dark tips. They are at least as long or longer than the cauda and taper slightly. The cauda is finger shaped, not constricted and the same colour as the basal part of the siphunculi. The body length of Nasonovia ribisnigri apterae is 1.3-2.7 mm.

Alate Nasonovia ribisnigri (see third picture above) have a conspicuous pattern of black abdominal markings. They have 23-66 secondary rhinaria on the third antennal segment, 2-14 on the fourth segment and none on the fifth segment.

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36.   Protaphis middletonii (Erigeron root aphid, corn root aphid, aster root aphid)

Western & Central North America. On more than 11 plant families.

Protaphis middletoni occur on the roots of plants in numerous families including the Asteraceae, Brassicaceae, Poaceae, Lamiaceae and Apiaceae. Oestlund (1887) found it very plentiful on the roots of horseweed (Erigeron canadensis), and more rarely on giant ragweed (Ambrosia trifida). As a pest it is particularly important on corn (Poaceae), sunflower, chrysanthemum & artichoke (Asteraceae), celery (Apiaceae), potato (Solanaceae), and beets (Chenopodiaceae). It has not been implicated in the transmission of any plant virus. Jensen noted that Aphis middletonii is highly variable in habits and appearance, feeding both underground and low down on the stem above ground. Colonies are usually ant-attended. Sexual forms may develop in autumn, but anholocyclic overwintering is probably also common. Protaphis middletoni is found throughout western and central North America. Aphids of this group are also recorded from Asteraceae in Brazil, and from prickly pear (Opuntia) roots in Australia and South Africa.

First image above by permission, copyright Claude Pilon, all rights reserved.
Second and third images above, copyright Andrew Jensen under a creative commons licence.

Adult apterae of Protaphis middletonii are pale green, bluish green, grey-green or olive-green, and more (see first picture above) or less (see second picture above) dusted with greyish wax. The apterae have 0-12 secondary rhinaria on antennal segment III. The antennal terminal process is 1.4-2.1 times as long as the base of antennal segment VI. The abdomen has dark marginal spots and also commonly some transverse black bands, but not an extensive solid black patch. Their legs are more or less dusky. The siphunculi are black, short, slightly thicker at base, and less than one tenth the body length. The cauda is also black and bluntly triangular. The body length of adult apterae is 1.5-2.5 mm.

Alatae have less apparent dark dorsal cross bands than the apterae. They have secondary rhinaria distributed 4-22 on segment III, 0-9 on segment IV, and 0-6 on segment V. Immature Protaphis middletonii are a somewhat paler green than the adults.

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37.   Brevicoryne brassicae (Mealy cabbage aphid)

Cosmopolitan. On 11 plant families.

The mealy cabbage aphid does not host alternate but spends its entire life cycle on cabbage (Brassica oleraceae) or other brassicas. In cold climates oviparae and small thin winged males occur in autumn, and the population overwinters as eggs. Where winters are mild Brevicoryne brassicae overwinters parthenogenetically. It has a cosmopolitan distribution.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

Brevicoryne brassicae apterae are green and covered with a greyish white mealy wax that is also secreted on the plant and spreads throughout the colony (see first picture above). The head, tips of the antennae and the legs are dark. Some abdominal segments have small sclerites and there are also intersegmental muscle sclerites. Their siphunculi are thick and very short, 0.06-0.07 times the body length. and 0.8-1.0 times the length of the cauda. The cauda is triangular and broad. The body length of Brevicoryne brassicae apterae is 1.9-2.7 mm.

The alate (see second picture above) is with her group of offspring. The alate Brevicoryne brassicae has a dark head and thorax, 50-70 secondary rhinaria on the third antennal segment, marginal sclerites and dark dorsal cross bands.

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38.   Lipaphis pseudobrassicae (Turnip aphid)

Cosmopolitan except Northern Europe. On more than 10 plant families.

The Turnip aphid does not host alternate. Lipaphis pseudobrassicae feeds on various members of the mustard family (Brassicaceae), and especially on Brassica crops. It lives on the undersides of leaves as well as on inflorescences, young shoots and growing points. Sexual morphs have been found in some countries, but in warm climates it is predominantly anholocyclic. Its distribution is cosmopolitan apart from parts of northern Europe. It is not recorded in Britain.

First image above: copyright Andy Jensen, Creative Commons (CC BY-NC-SA 2.0).
Second image copyright Claude Pilon, all rights reserved.

Adult apterae of Lipaphis pseudobrassicae (see picture above) are small to medium sized yellowish green, grey green or olive green aphids, with a slight white wax bloom. In humid conditions they may be more densely coated with wax. There are two longitudinal rows of dark bands on the thorax and abdomen which unite into a single band near the tip of the abdomen. The combined length of antennal segment III and the terminal process is usually more than 2.4 times as long as the siphunculus (cf. Lipaphis erysimi, which has the combined length of those segments usually less than 2.4 times the length of the siphunculus). The siphunculi are pale with dark tips and are about as long as the antennal terminal process. The body length of adult Lipaphis pseudobrassicae apterae is 1.4-2.4 mm.

Lipaphis pseudobrassicae alatae have a dusky green abdomen with conspicuous dark marginal sclerites, and dusky wing veins. Their antennae have 15-30 secondary rhinaria on segment III, 3-13 on IV and 0-3 on V.

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39.   Cavariella aegopodii (Willow - carrot aphid)

Cosmopolitan. On 10 plant families.

The willow-carrot aphid host alternates from willows (Salix spp.) to umbellifers (Apiaceae). The preferred primary hosts are crack willow (Salix fragilis) and white willow Salix alba, although some willow species seem only to be colonized in spring by winged forms from populations which have overwintered parthenogenetically. Preferred secondary hosts are cultivated umbellifers such as carrots (Daucus carota) and fennel (Foeniculum vulgare) plus several wild umbellifers. Cavariella aegopodii is widespread throughout temperate and warm temperate parts of the world.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

Cavariella aegopodii apterae are small and greenish or reddish. The tips of their antennae and apices of the legs are brownish. The antennae are about 0.4 times the body length, with the terminal process about 0.85-1.3 times the basal part of segment VI (cf. Cavariella archangelicae, Cavariella konoi, Cavariella pastinacae and Cavariella theobaldi which all have the terminal process more than 1.3 times the length of the basal part of segment VI). Cavariella aegopodii siphunculi are swollen and about twice as long as the cauda. The supracaudal process is 0.75-1.05 times the cauda, broadest at the base and oblong triangular to conical. The body length of apterae is 1.5-2.8 mm.

The alate of Cavariella aegopodi has a central black patch on the abdominal dorsum, and a dark cauda and siphunculi. As with the aptera, it is best distinguished from the other common Cavariella species by its short terminal antennal process which is less than 1.5 times longer than the base of antennal segment VI.

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40.   Rhopalosiphum maidis (Corn leaf aphid)

Cosmopolitan in warmer climates. On more than 8 plant families.

Rhopalosiphum maidis populations are anholocyclic on grasses (Poaceae) in most parts of the world, but in parts of Asia (where Rhopalosiphum maidis originated) it host alternates with Prunus spp. as the primary host. It only occurs sporadically in cool temperate climates such as Britain and southern Scandinavia, but is cosmopolitan in warmer climates, where it can be an important pest of cereals. Rhopalosiphum maidis are commonly attended by ants which consume the abundant honeydew.

First two images above copyright Mihajlo Tomić, all rights reserved;
Third image copyright Brendan Wray,AphID, USDA APHIS PPQ, Bugwood.org under a Creative Commons License.

Adult apterae of Rhopalosiphum maidis (see first picture above) are elongate-bodied olive green to bluish-black aphids, sometimes dusted with wax. The areas around the bases of the siphunculi and often other parts of the dorsum are a darker green or purplish black (cf. Rhopalosiphum padi which has a rusty red suffusion around the siphuncular bases). The antennae are dark except for segment III and part of IV, and the terminal process is 1.7-2.8 times the length of the base of antennal segment VI. The apical segment of the rostrum (RIV+V) is about 0.8 times the length of the second hind tarsal segment (HTII). The siphunculi are dark and rather short, not flared at the apex and only 1.1-1.4 times the length of the cauda. Immature Rhopalosiphum maidis are usually a somewhat lighter blue-green, with clearly marked darker areas around the bases of the siphunculi.

The alate Rhopalosiphum maidis (see second picture above) has a yellow-green to dark green abdomen with darker areas around the bases of the siphunculi, but no other dorsal dark markings anterior to the siphunculi.

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41.   Hyadaphis coriandri (Coriander aphid)

Cosmopolitan in warm temperate climates. On 7 plant families.

The primary host of Hyadaphis coriandri in west Asia is honeysuckle (Lonicera spp.), although the species is anholocyclic over much of its range. All the progeny of the fundatrix migrate to the secondary host, numerous species & genera of Apiaceae including coriander (Coriandrum), cumin (Cuminum), and carrot (Daucus). They feed mostly on the umbels. Coriander is particularly susceptible to attack. Occasionally plants outside the Apiaceae are colonised, such as mint (Mentha, Lamiaceae), amaranth (Amaranthus, Amaranthaceae), and soy bean (Glycine max, Fabaceae). It has not been implicated in the transmission of any plant virus. Hyadaphis coriandriis probably of West Asian origin where the holocycle still exists. Hyadaphis coriandri now occurs in Southern Europe, the Mediterranean region, the Middle East, Central & South Asia, and Africa, and has more recently been introduced to the United States in Florida, California & Hawaii, and to South America in Argentina & Peru.

First image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka (accessed 12/2/20);
second image of clarified mounts, above, copyright Brendan Wray under a Creative Commons License.

Adult apterae of Hyadaphis coriandri are rather small, broadly oval, rather short-legged, mainly dirty greenish with dark-green dorsal mottling and rust-red patches around the bases of short, dark-brown siphunculi. The body is variably dusted with white mealy wax. Their antennae are 0.39-0.4 times as long as the body, with the terminal process twice the length of the base of last antennal segment. The siphunculi are 0.78 times as long as the cauda, and strongly swollen at the base. The cauda bears 6-7 hairs. The body length of adult apterae is 1.3-2.1 mm.

The alate Hyadaphis coriandri have pale-green abdomen with black dorsal markings, and reddish-brown patches around the siphuncular bases.

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42.   Dysaphis tulipae (Tulip aphid)

Cosmopolitan. On 7 plant families.

The tulip bulb aphid is found on the bulbs, shoots and leaves of many monocotyledonous plants in the lily and tulip (Liliaceae), crocus, gladiolus and iris (Iridaceae), arum (Araceae) and banana (Musaceae) families. The species is entirely parthenogenetic, no sexual forms have been recorded. Their colonies are commonly ant attended. Dysaphis tulipae has a worldwide distribution, apart from South America.

Adult apterae of Dysaphis tulipae (see first picture above) are pale greenish yellow, but may appear whitish because of an overlay of white powder. There is often a reddish suffusion around the siphunculi which is more prominent in immatures (see second picture above). The longest hairs on the third antennal segment are 10-27 μm, often somewhat blunt apically, and 0.6-1.1 times longer than the basal diameter of that segment. There are spinal tubercles on the head and on abdominal tergite 8. The siphunculi are 1.5-2.0 times the caudal length and are slightly thickened in the middle. The body length of the Dysaphis tulipae aptera is 1.7-2.3 mm.

The alate Dysaphis tulipae (see first picture above) has a dorsal patch with lateral extensions which close the space between it and the prominent marginal sclerites. The antennae have 24-55 secondary rhinaria on the third antennal segment, 3-14 on the fourth segment, and none on the fifth.

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43.   Greenidea psidii (Hairy-tailed guava aphid)

On 6 plant families.

Greenidea psidii feeds on the young shoots and undersides of young leaves of guava (Psidium guajava) and other Myrtaceae (Rhodomyrtus, Eugenia, Melaleuca, Plinia). It is a pest of considerable importance on guava, but has not been implicated in the transmission of any plant virus. It may be restricted to Myrtaceae, but similar aphids occur on other plants such as Ficus and Engelhardtia. Sexual morphs are unrecorded, and parthenogenetic morphs occur all-year-round in some countries. Greenidea psidii is originally Indo-Asian, including the Philippines, Sumatra, Taiwan, and Australia. It has been introduced into the Western Hemisphere, and is now present in North, Central & South America.

First image above copyright Jesse Rorabaugh , second image copyright Aphidnet;
both under a public domain (CC0) licence.

Adult apterae of Greenidea psidii are pear-shaped, shiny dark reddish or yellowish brown. The siphunculi are yellowish brown, darker at the base and apex, and curved outwards distally. The siphunculi are 0.26-0.42 times the body length, have reticulation only at their bases, and are ornamented with irregularly spaced spinules.

Alatae of Greenidea psidii have 20-31 secondary rhinaria, some crowded and not in line with the others, and often touching. The siphunculi are 0.66-0.77 times the body length.

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44.   Macrosiphum pallidum (Pink wild rose aphid)

On 6 plant families.

Macrosiphum pallidum is most commonly found on various wild rose (Rosa) species and various other Rosaceae including agrimony (Agrimonia), strawberry (Fragaria), Geum, and Potentilla). It also appears to be able to colonise a wide range of other plants, such as Eupatorium (Asteraceae), Cicuta (Apiaceae) and Chenopodium (Chenopodiaceae). It has not been implicated in the transmission of any plant virus. The life cycle is unknown. Macrosiphum pallidum is widespread in North America.

First image above copyright David Voegtlin, Discover Life
second image above copyright Aphidnet both under a Creative Commons License.

Adult apterae of Macrosiphum pallidum (see pictures above) are pink or green , with the antennae, femoral apices, tibiae, and tarsi dark (cf. Macrosiphum impatientis which has antennal segment III mainly pale, and the tibiae with pale middle sections). The siphunculi are dark, except at the extreme bases (cf. Macrosiphum rosae which has the siphunculi entirely dark). Apterae have 3-14 secondary rhinaria on antennal segment III. The body length of adult apterae is 2.1-4.6 mm.

Alatae of Macrosiphum pallidum have 14-22 secondary rhinaria on antennal segment III.

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45.   Aphis eugeniae (Butternut euphorb aphid)

East & South-east Asia, Australia, North America On 5 plant families.

Aphis eugeniae is most commonly found on woody Euphorbiaceae, such as butternut tree (Glochidion), Breynia, and Phyllanthus. However the species is quite polyphagous, and has also been found on plants in various other families such as Chromolaena (Asteraceae), Convolvulus (Convolvulaceae), Dipsacus (Dipsacaceae), Hibiscus (Malvaceae), Eugenia (Myrtaceae) and Pyrus & Eriobotrya (Rosaceae). It is not thought to be involved in the transmission of any plant virus. Aphis eugeniae is native to east and south-east Asia and Australia. More recently it has been found on Eriobotrya japonica in Hawaii and Florida.

Both images above copyright Aphidnet under a Creative Commons License.

Adult apterae of Aphis eugeniae are orange-yellow to brownish-orange with black siphunculi and cauda. The hind tibiae are only dark towards the apices. The antennal terminal process is 2.5-3.5 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is 1.1-1.3 times the base of the second hind tarsal segment (HTII). It has modified, peg-like hairs on the hind tibiae. Hairs on the first tarsal segment are distributed (from fore leg to hind leg) 3:3:3 (cf. Aphis spiraecola, which has hairs on the first tarsal segments distributed 3:3:2). The cauda is black with 9-22 hairs. The body length of adult apterae is 1.3-2.1 mm.

Alatae of Aphis eugeniae have 5-10 secondary rhinaria on antennal segment III, and 0-1 on IV.

46.   Uroleucon ambrosiae (New England aster aphid)

North America. On 5 plant families.

In eastern and northern USA, and Canada, Uroleucon ambrosiae is mainly found on Ambrosia and Iva. However, populations in south-western USA, and Central and South America are far less specific, having been found feeding on the leaves and flower-stems of many additional genera in the Asteraceae including Achillea, Aster, Cichorium, Eupatorium, Lactuca, Rudbeckia and Senecio. The more polyphagous form is sometimes regarded in South America as a subspecies, Uroleucon ambrosiae ssp. lizerianum. The species is monoecious holocyclic in temperate North America with alate males, but it is usually anholocyclic in southern USA, and Central and South America.

First two images above, copyright Jesse Rorabaugh, no rights reserved
Third image copyright Brendan Wray under a Creative Commons License.

Adult apterae of Uroleucon ambrosiae are red-brown to dark brown or dull red (see two pictures below), with black siphunculi and a pale cauda. The antennae are dusky to black, but paler on antennal segments I, II and the base of III, with 14-27 secondary rhinaria on segment III, and a terminal process which is 5.5-6.5 times the base of antennal segment VI (cf. Uroleucon leonardi, which has a terminal process 6.3-7.2 times the base of segment VI). The rostrum fully reaches the third pair of coxae, with the apical rostral segment (RIV+V) longer than the base of antennal segment VI. There are dusky scleroites on the dorsum of the abdomen. Abdominal marginal tubercles are absent (cf. Macrosiphum nigrotuberculatum, which has small black marginal abdominal tubercles). The hind tibia usually has a pale or dusky basal section, but this not as pale as the cauda for more than 0.5 of its length (Uroleucon ivae on Ambrosia & Iva, which has the tibia as pale as the cauda for more than 0.7 of its length). The second hind tarsal segment (HTII) is 0.9-1.1 times the length of RIV+V (cf. Uroleucon pseudoambrosiae, which has HTII 0.7-0.85 times RIV+V). The siphunculi are 1.1-1.3 times the length of the cauda, have a third of their length with polygonal reticulation, and are uniformly dark (cf. Uroleucon rudbeckiae, whose siphunculi are much paler at the base). The pale cauda tapers to a rather acute point, and bears 7-8 hairs on each side. The Uroleucon ambrosiae aptera body length is 2.5-3.5 mm.

The Uroleucon ambrosiae alate vivipara is coloured similarly to the aptera, apart from having dark brown thoracic lobes and a dark blotch on tergite VI posterior to the base of each siphunculus. The antennae are entirely black, with 31-45 secondary rhinaria on antennal segment III. The rostrum hardly reaches the third pair of coxae. The dusky abdominal scleroites are often reduced or lacking.

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47.   Neotoxoptera oliveri (Endive root aphid)

Almost cosmopolitan. On 4 plant families.

Neotoxoptera oliveri is particularly important on monocots such as endives (Cichorium, Alliaceae), Caryophyllaceae (Stellaria), and violets (Violaceae), but also attacks Dianthus and Stellaria (Caryophyllaceae) and Portulaca (Portulaceae), a host range remarkably similar to that of Myzus ascalonicus. It was originally described from the roots of endives, where it can be a major pest. It seems to be anholocyclic everywhere, although one male has been recorded. The species is almost cosmopolitan, now being found in southern Europe, Africa, Pakistan, Korea, Java, Australia, New Zealand, Mexico, Central & South America.

Both images above copyright Aphidnet under a Creative Commons License.

Adult apterae of Neotoxoptera oliveri are dark-red to almost black. The antennal terminal process is 3.5-4.8 times the base of antennal segment VI. The apical rostral segment (RIV+V) is 1.2-1.4 times the second hind tarsal segment (HTII). The body length of adult apterae is 1.1-2.0 mm.

Alatae of Neotoxoptera oliveri have a black central dorsal abdominal patch. The wing veins are heavily black-bordered, the borders widening out at the base and apex of each vein (cf. Neotoxoptera formosana, where the borders on the wing veins are of rather constant width along the full length of the vein).

48.   Prociphilus erigeronensis (Ragweed root aphid)

North America. On 4 plant families.

Prociphilus erigeronensis lives in ant-attended colonies on roots of many plants. It is particularly important on ragweed (Ambrosia), Aster, and lettuce (Lactuca (Asteraceae), grasses & cereals (Agrostis, Poa, and Triticum) (Poaceae), and peanuts (Arachis), beans (Phaseolus), and clover (Trifolium) (Fabaceae), but also attacks Crataegus (Rosaceae), and a variety of other ornamentals. It is possible that Crataegus or Amelanchier function as a primary host for this species in some areas, but most populations are anholocyclic. It has not been implicated in the transmission of any plant virus. The species is widely distributed in North America, although the name may be being applied to more than one species.

First & third images above copyright Aphidnet; second image above copyright CBG Photography Group;
all under a Creative Commons License.

Adult apterae of Prociphilus erigeronensis are white to pale yellow with darker head, antennae, legs, and end of abdomen. In life they are covered in white wax. Wax pore plates are present on the head thorax and abdomen, but are especially well developed marginally on the abdomen. The antennal terminal process is very short, less than 0.5 times the base of antennal segment VI. Siphunculi are absent. The cauda and anal plate form a dark rounded posterior projection of the abdomen. The body length of adult apterae is 1.7-2.3 mm.

49.   Aphis asclepiadis (Dogwood-milkweed aphid)

North & South America. On 3 plant families.

Aphis asclepiadis is now known to host alternate with a sexual phase on dogwood (Cornus spp.) where in spring they twist and curl the leaves. In late spring / early summer they migrate to a wide range of summer hosts in the Asteraceae, Apiaceae and Apocynaceae. The dogwood-milkweed aphid is usually attended by ants. Aphis asclepiadis is found throughout USA and Canada, and has been introduced to South America (Brazil, Peru and Argentina).

First two images above by permission, copyright Claude Pilon, all rights reserved;
Third image above copyright Brendan Wray under a Creative Commons Attribution-Noncommercial 3.0 License.

Adult apterae of Aphis asclepiadis on their primary host, dogwood (Cornus), in spring, are dark yellow to green - with their siphunculi variably coloured from green to black. Apterae on the secondary hosts (mainly Asteraceae, Apiaceae and Apocynaceae) are pale green, yellowish green or deep olive green mottled with yellowish green - with black siphunculi (see first picture above). The abdominal dorsum usually has no dark markings anterior to the siphunculi apart from a few dark intersegmental sclerites (cf. Aphis fabae, which usually has some dark markings anterior to the siphunculi in addition to intersegmental sclerites). The third antennal segment is 1.05-1.95 (usually more than 1.3) times the length of the terminal process. The hind tibiae are pale for more than half their length (cf. Aphis nerii, which has entirely dark or dusky hind tibiae). Tergite VIII usually has 4-6 hairs (it ranges from 2-6) (cf. Aphis gossypii and Aphis spiraecola, which have 2 hairs (rarely 3) on tergite VIII). The siphunculi are 1.5-2.9 times as long as the cauda. The body length of adult apterae is 1.4-2.5 mm. Immature Aphis asclepiadis vary in colour from blue-green to yellow-green to yellow-orange, and fourth instar alatoid nymphs usually have a set of white wax spots.

The alate Aphis asclepiadis (see second picture above) has a green or yellow-green abdomen, dark intersegmental and marginal sclerites, postsiphuncular sclerites, and bands across tergites VII-VIII. Alatae have 15-40 secondary rhinaria on antennal segment III, & 0-2 on segment IV.

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50.   Aphis glycines (Soybean aphid)

Asia, North America. On 3 plant families.

Aphis glycines is native to Asia where its main primary hosts are Dahurian buckthorn (Rhamnus davurica) and Japanese buckthorn (Rhamnus japonica). Aphis glycines host alternates, mainly to soybean and other wild Glycine species, and a few other members of the Fabaceae. In July 2000 it was first found in North America in Wisconsin. It rapidly proved to be highly invasive and by 2007 had been found in 20 states. In America the main primary hosts are purging buckthorn (Rhamnus cathartica) and alderleaf buckthorn (Rhamnus alnifolia). Aphis glycines has not been found utilising the European alder buckthorn (Rhamnus frangula) in America despite it being a common invasive there, which may explain why this aphid has not yet been found in Europe. On soybean Aphis glycines feeds on the stems and leaf undersides. In Asia it is found in China, Indonesia, Japan, Korea, Malaysia, the Philippines and Thailand. In America Aphis glycines is found primarily in the middle to high latitudes in the midwest of the USA, and in Ontario and Quebec provinces in Canada.

First image above copyright Ho Jung Yoo, Purdue University; all use allowed providing attribution given.
Second image above copyright Christina DiFonzo under a Creative Commons Attribution 3.0 United States license.
Third image courtesy Favret, C. & G.L. Miller, AphID.

Adult apterae of Aphis glycines (see first picture above) range from pale yellow to lime green in colour, commonly green mottled with pale yellow. On late season soybeans, some aphids may be much smaller and paler than usual. The insect's head is pale, as are the basal antennal segments, and the antennal tubercles are weakly developed. The siphunculi are dark except at their bases (cf. Aphis nasturtii which has the siphunculi usually rather pale, only darker at the apices). The cauda is very pale, usually with a slight midway constriction, more than 3 times longer than its narrowest width at midlength, and usually bearing 7-9 hairs (cf. Aphis gossypii for which the cauda is pale to dusky, without a constriction, less than 3 times longer than its width at midlength, and usually bearing 5-6 hairs). The body length of adult Aphis glycines apterae is 1.2-1.7 mm.

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51.   Hyadaphis foeniculi (Fly honeysuckle aphid, Fennel aphid)

Europe, West Asia, North & South America. On 3 plant families.

Hyadaphis foeniculi host alternates. It mainly uses fly-honeysuckle (Lonicera xylosteum) as its primary host. Infested leaves are curled upwards in spring. Hyadaphis foeniculi migrates to various Apiaceae where it feeds on stems, leaves and flowers. Its secondary hosts include hemlock (Conium), fennel (Foeniculum) and Pastinaca. Hyadaphis foeniculi is widespread in Europe, especially in the north. Hyadaphis foeniculi extends eastwards to Turkey and Iraq and is also found in North America and Brazil.

Third image above by permission of Roger Blackman, copyright AWP all rights reserved.

Hyadaphis foeniculi apterae on the primary host are greyish-green or light green with the middle part of the dorsum darker green (see first picture above). Their colour is rather more variable on the secondary host and reddish brown patches are often present at the siphuncular bases (see second picture above). The legs and antennae of Hyadaphis foeniculi are dark. The prosternal sclerite is 1.4 to 2.6 times wider than long. The siphunculi are black and slightly swollen and are 1.05-1.4 times the length of the cauda. The body length is 1.3 to 2.6 mm on the primary hosts, 1.4-2.0 mm on the secondary hosts.

The alate often has 1-4 secondary rhinaria on the fifth antennal segment.

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52.   Uroleucon compositae (Safflower aphid, Marigold aphid)

On 3-4 plant families.

Uroleucon compositae feed on the flower-stems (and in low numbers along the mid-ribs of the leaves) of a wide range of Asteraceae. They favour plants growing in moist or shady situations at the end of the dry season. It is a pest of Carthamus tinctoria (safflower) in India, and is common on herbaceous Vernonia after the rains in Africa. It also occurs on plants in the mallow (Malvaceae), mulberry (Moraceae) and passionfruit (Passifloraceae) families. It may transmit at least two plant viruses. It seems to be anholocyclic everywhere, with no sexuales known. Uroleucon compositae is found in tropical and subtropical climates, especially in Africa, on the Indian subcontinent, and also in West Asia, Réunion, Mauritius, Taiwan, Brazil & Surinam. It does not occur in south-east Asia.

First image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka (accessed 12/2/20).
second image copyright Aphidnet under a Creative Commons License.

Adult apterae of Uroleucon compositae are shining very dark red to almost black, with long black siphunculi and cauda. The middle part of the hind tibia is pale (cf. Uroleucon aeneum & Uroleucon jaceae, which both have the middle part of the hind tibiae dusky or dark). The body length of adult apterae is 1.9-4.1 mm.

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Acknowledgements

Our especial thanks to all those who gave us permission to reproduce their images, or made them available as creative commons, their copyright is acknowledged beneath the image as shown above.

We have used the keys and species accounts of Blackman & Eastop (1994) supplemented by information from Favret & Miller (2012). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

  • Blackman, R. & Eastop, V. F. (1984). Aphids on the World's Crops: An Identification and Information Guide. Wiley. 466 pp (p 13)

  • Blackman, R.L. & Eastop, V.F. Aphids on the world's plants An online identification and information guide. Full text

  • Favret, C. & Miller, G.L. (2012). AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. [AphidNet.org Accessed September 2022].