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Oak and chestnut aphidsOn this page: Myzocallis asclepiadis boerneri carpini castanicola coryli granovskyi myricae punctata schreiberi tuberculata walshii
Genus Myzocallis [Panaphidini]
Myzocallis are small, delicate, usually yellowish aphids. In most species the adult viviparae are all winged. Antennal tubercles are weakly developed, and the front of the head is convex. Antennae are 6-segmented with an elongate terminal process. The forewings have normal venation with a 3-branched media; the branches of the cubitus are separated at the base and slightly divergent. The wings are variably pigmented, but there is generally at least a dark spot at the base of the pterostigma. The siphunculi are short and stump shaped and are not flared at the apex. The cauda is knobbed and the anal plate is bilobed. Immatures usually have long, capitate dorsal hairs.
The Myzocallis genus comprises about 40 species living on oaks and chestnuts (Fagaceae). They have a sexual stage in the life cycle, but do not host alternate and are not attended by ants. They are found in North America, Europe and Asia and have been introduced to Australia and South America.
Myzocallis asclepiadis (Common milkweed aphid)
In spring immatures are pale green, but as summer progresses an increasing proportion of immatures are marked with yellow, orange or red blotches on the dorsum (see first picture below), with some individuals appearing more uniformly red or orange. They have numerous long capitate hairs borne on paired spinal and marginal tubercles. All adult viviparae of Myzocallis asclepiadis are alate. The alate Myzocallis asclepiadis vivipara is very distinctive (see second picture below). The body is yellow-green or brown green with blotches of red, orange or yellow, overlain with a complex set of black markings including narrow dorsal bands. The wings are conspicuously mottled between the veins with brownish or blackish patches, with the markings not restricted to the bordering of the veins or the costal area. The antennae are pale but ringed with black. The siphunculi and areas around their bases are pale. The cauda is knobbed and the anal plate is bilobed.
Images above by permission, copyright Claude Pilon, all rights reserved.
Myzocallis asclepiadis is found on the undersides of leaves of milkweed (Asclepias species) especially common milkweed (Asclepias syriaca). Sexual forms develop in October, and the population overwinters in the egg stage. It is very common in all parts of Illinois. The common milkweed aphid is found in eastern USA and Canada.
Myzocallis boerneri (Turkey oak aphid)
Immature Myzocallis boerneri (see first picture below) are pale yellow with paired, dusky, rather indistinct spinal and marginal spots. Winged adults of Myzocallis boerneri (see both pictures) are yellowish, with the head and thorax sometimes partly dusky. Their dorsal abdomen has small paired spinal and marginal specks of brown pigment. The antennae are pale but ringed with brown-black. The length of the last segment of the rostrum (RIV+V) is 0.84-1.25 times the length of the second segment of the hind tarsus (HTII) (cf. Myzocallis schreiberi in which the length of RIV+V is 1.2-1.5 times the length of HTII). The body length of Myzocallis boerneri apterae is 1.3-2.2 mm.
The Turkey oak aphid lives on the undersides of leaves of several oak (Quercus) species, especially the Turkey oak (Quercus cerris), but also holm oak (Quercus ilex) and sessile oak (Quercus petraea). Myzocallis boerneri is widely distributed in Europe, the Middle East, and has been introduced to New Zealand, California and Argentina.
Myzocallis carpini (Hornbeam aphid)
Immature Myzocallis carpini (see first picture below) are unmarked, and have the body hairs (and a few basal antennal hairs) capitate, and very much longer than those of the adult. Winged adult Myzocallis carpini viviparae (see second picture below) are pale yellow to yellowish white, with no dorsal abdominal markings. The forewing has a black spot at the base of the pterostigma. Their antennae are ringed with black, and antennal segment VI is 4.4 to 5.3 times as long as the apical rostral segment. The apical rostral segment is at most 1.02 times as long as the second hind tarsal segment. The body length of alate Myzocallis carpini is 1.3-2.2 mm.
The hornbeam aphid is found on the undersides of leaves of hornbeam (Carpinus betulus), especially when used for hedging. Myzocallis carpini is found in Europe, North Africa, the Middle East, and has been introduced into New Zealand and North America.
Myzocallis castanicola (Sweet chestnut aphid)
Immature Myzocallis castanicola (see first picture below) are yellowish or greenish with some brown-black dorsal markings. Winged adults of Myzocallis castanicola (see second picture below) are yellow with the wing venation distinctly outlined in brown and forewing veins ending in brown spots (cf. other oak-feeding Myzocallis whose wings are not distinctly outlined in brown). They are distinctively marked with a dark median strip on the head and thorax, and paired black spinal and marginal patches on the dorsal abdomen. Their antennae are dark beyond the basal half of the third antennal segment. The tips of the tibiae and tarsi are dark, as are the forewing veins which end in fuscous spots. The siphunculi are also dark. The body length of Myzocallis castanicola alates is 1.6-2.3 mm.
The sweet chestnut aphid is found on the undersides of leaves of many chestnut (Castanea) and oak (Quercus) species. Myzocallis castanicola is found in Europe, Middle East, southern Africa, Australia, South America and western North America.
Myzocallis coryli (Hazel aphid)
Immature morphs (see first picture below) have the body hairs, and sometimes a few basal antennal hairs, capitate and very much longer than those of adult viviparae. Winged adult viviparae of Myzocallis coryli (see second picture below) are pale yellow to yellowish white. Their antennae are ringed with black, with a terminal process that is 2.05-2.55 times the length of the basal part of antennal segment 6. The forewing has a black spot at the base of the pterostigma. The body length of Myzocallis coryli alates is 1.3-2.2 mm.
Myzocallis coryli oviparae are orange-yellow in colour, but when examined in alcohol they appear quite pale. Like the immatures, the oviparae have long capitate hairs.
The hazel aphid lives on the undersides of leaves of hazel (Corylus species). Like Myzocallis carpini, it may become abundant when its host is used for hedging. Myzocallis coryli is found in Europe, south-west Asia, north Africa, Japan, New Zealand, western North America, and South America.
Myzocallis granovskyi (Longtailed oak aphid)
Immature Myzocallis granovskyi (not pictured) are pale yellow with a grey waxy bloom, dark dorsal patches and dark tibiae. All adult viviparae of Myzocallis granovskyi are alate and coloured yellow to orange-yellow. The species is a member of the black-bordered oak aphid group (subgenus Lineomyzocallis), characterized by the costal margin of the forewing usually having a characteristic continuous band of black pigment extending beyond the pterostigma to the wing tip. The thorax is rather pale, except that the lateral margins of the pronotum usually each have a conspicuous dark longitudinal stripe, continuing on the mesonotum to the base of the forewing (but note: spring generations of Myzocallis granovskyi may have much reduced pigmentation. The antennae are shorter than body and are pale apart from black rings around the apices of segments III-VI. The femora are black on the distal third (cf. Myzocallis bella, Myzocallis melanocera and Myzocallis neoborealis, which all have the femora black over at least half the length; and cf. Myzocallis walshii, which has entirely pale femora). The tibiae of all legs are black (cf. Myzocallis ephemerata, Myzocallis exultans, Myzocallis multisetis, Myzocallis longirostris & Myzocallis walshii, which have only the fore-tibiae very dark or black, distinctly darker than the mid and hind tibiae). The cauda has an elongate "neck". The body length of alate Myzocallis granovskyi viviparae is 1.8-2.3 mm.
Both images above copyright Tom Murray under a Creative Commons Attribution License.
Myzocallis granovskyi does not host alternate. It feeds only on a few oak (Quercus) species. Unlike most other species of Myzocallis on oak, it usually feeds on the upper sides of leaves. Sexual forms develop in October and the oviparae deposit overwintering eggs on oak. Myzocallis granovskyi is found throughout eastern USA, and has been collected once in the west (Oregon). It is also found in Ontario and Quebec in Canada.
Myzocallis myricae (Bog myrtle aphid)
Immature bog myrtle aphids are bright yellow with longitudinal rows of pale centred dark spots. Adult Myzocallis myricae alates are yellow or orange, with additional black longitudinal markings on the head and thorax. The antennae of bog myrtle aphids are shorter than their body, and the terminal process of their sixth antennal segment is less than twice the length of its basal part. The abdominal tergites 1 to 7 have paired dusky spinal and marginal sclerites. Myzocallis myricae siphunculi are short truncated cones. The tibiae have similar pigmentation to distal parts of the femora. Their body length is less than 3.5 mm.
Myzocallis myricae does not host alternate but feeds only on bog myrtle (Myrica gale). Sexual forms occur in autumn. It is largely restricted to northern and western Europe.
Myzocallis punctata (Regular oak aphid)
Immatures of Myzocallis punctata are yellow with a variably developed pattern of brownish pigmented areas around the bases of their spinal and marginal setae. All adult viviparae are alate. Adult alatae of Myzocallis punctata (see pictures below) are generally described as being yellow, but the lateral parts of the dorsum may also be suffused with pink. Dark dorsal body markings are often present but these markings are seasonally variable, and may be absent. Their antennae are ringed with black, and the legs are mainly pale. The apical rostral segment (RIV+V) is 0.80-0.95 times as long as the second hind tarsal segment (HT II) (cf. Myzocallis asclepiadis on milkweed, which has RIV+V 1.03-1.17 times the length of HT II). The forewings are variably pigmented, sometimes almost hyaline in early spring populations except for dark spots at ends of veins, but later with a distinctive pattern of patchy infuscation. Abdominal tergites I & II may or may not bear small paired wart-like spinal processes not more than 0.5 × their basal widths (cf. Myzocallis tuberculata, which has low paired spinal processes on abdominal tergites I & II in spring populations, and much longer conical or finger-like processes in summer populations). The siphunculi are pale, with spiculose ornamentation (cf. Myzocallis discolor on oak, which has dark siphunculi on dark siphuncular sclerites). The anal plate is deeply indented and the cauda is knobbed. The body length of adult Myzocallis punctata viviparae is 1.8-2.5 mm.
Myzocallis punctata is one of the most common oak aphids in North America, and can be found on many different oak (Quercus) species, especially of the white oak group. It does not host alternate. In north east USA sexuales occur in the autumn, and overwintering eggs are laid on the oak twigs. In California parthenogenetic viviparae are present all year. Myzocallis punctata is native to eastern North America, but has been introduced into western states.
Myzocallis schreiberi (Holm oak aphid)
Immature Myzocallis schreiberi (see first picture below) are whitish to pale straw yellow with four longitudinal rows of dark spots and long body hairs. Winged adult viviparae of Myzocallis schreiberi (see second picture below) are pale yellow, with the head and the thorax slightly darker. The prothorax often has short lateral streaks of dark pigment. The dorsal abdomen has small transversely oval, dark spinal spots and paler marginal sclerites. The length of the last segment of the rostrum (RIV+V) is 1.2-1.5 times the length of the second segment of the hind tarsus (HTII) (cf. Myzocallis boerneri in which the length of RIV+V is 0.84-1.25 times the length of HTII). The legs are mainly pale and the siphunculi are usually dark. The body length of Myzocallis schreiberi apterae is 1.3-2.2 mm.
The holm oak aphid lives on the undersides of leaves of holm oak (Quercus ilex) and only rarely on other oaks. Sexual morphs are unknown, and viviparous forms can be found throughout the year. Myzocallis schreiberi is distributed through western and southern Europe.
Myzocallis tuberculata (Tuberculate oak aphid)
Immature Myzocallis tuberculata (see first picture below) are pale yellow with dark spinal spots and patches of intense red pigment. They have long, capitate dorsal hairs. All adult viviparae of Myzocallis tuberculata are alate (see second picture below). They are coloured reddish-pink to pinkish-yellow, and have patches of white wax powder, small dark markings on and around their dorsal tubercles, and dark intersegmental dorsal sclerites. Their antennae are pale, but ringed with black. The forewings have pigmentation thickly bordering all veins, sometimes extending between veins. There are paired spinal tubercles on abdominal tergites I-VI. In spring populations the dorsal tubercles are all short - only about 0.75 times as long as their basal width. In summer/autumn (see two pictures below) the tubercles on I & II are much larger, up to 0.14 mm in length on abdominal segment I and sometimes pigmented (cf. Myzocallis punctata, which may have very short paired tubercles on tergites I - II, not more than half as long as their basal widths). The siphunculi are pale and short with spicules, and lack an apical flange. Like Myzocallis granovskyi, they have a knobbed cauda and a deeply bilobed anal plate. The body length of adult alate Myzocallis tuberculata is about 1.5 mm.
Myzocallis tuberculata does not host alternate, but feeds only on a few oak species (Quercus spp.), especially American white oak (Quercus alba), bur oak (Quercus macrocarpa) and chinquapin oak (Quercus muehlenbergii). Alate fundatrices were found in Minnesota in May, and oviparae have been recorded in Quebec on Quercus macrocarpa in late August. Myzocallis tuberculata is found in eastern USA and Canada.
Myzocallis walshii (Black-bordered oak aphid)
Immature Myzocallis walshii (see first picture below) bear numerous long capitate hairs, and lack pigmentation on the nymphal head, wing pads and femora (cf. Myzocallis exultans, whose immatures have some pigmentation). Myzocallis walshii immatures generally bear little or no pigment on their dorsum, but nymphs from some locations have prominent dorsal, lateral, and sublateral abdominal patches.
All adult viviparae of Myzocallis walshii are alate (see second picture below). The costal margin of the forewing usually has a continuous band of pigment extending beyond the pterostigma to the tip of the wing. The thorax is rather pale except that the lateral margins of the pronotum have conspicuous dark longitudinal stripes, continuing on the mesonotum to the base of the forewing. The antennal terminal process is 1.7 to 2.9 times the length of the base of antennal segment VI (cf. Myzocallis longiunguis, whose terminal process is more than three times the length of the base of antennal VI; and Myzocallis multisetis, whose terminal process is usually less than l.5 times the length of the base of antennal VI). The marginal tubercles on abdominal tergites II-IV are generally unpigmented except in some late season alatae. Myzocallis walshii generally lack pigment on their femora (cf. Myzocallis exultans, whose alates have pigmented femora). The fore tibiae of alate Myzocallis walshii are much darker than their middle and hind tibiae, and the tibiae bear darker pigmentation at the tips than proximally (cf. Myzocallis granovskyi, which has all its tibiae black, and lives on the upper leaf surface). The siphunculi are short and smooth without an apical flange, and the cauda is knobbed. The body length of adult Myzocallis walshii alatae is 1.6-2.0 mm.
Both images above by permission, copyright Claude Pilon, all rights reserved.
Myzocallis walshii lives on the leaf underside of various species in the red oak group (Quercus section Lobatae). It does not host alternate. Sexual forms develop in autumn, and the species overwinters as eggs. Myzocallis walshii is common throughout eastern North America and was introduced to the west coast, where it has been found on the native live oak (Quercus agrifolia) and on planted red oak in Oregon, Washington and British Columbia. In 1989 it was found on Quercus rubra planted in France, and has since spread to most of Europe. In Britain, it has been found on Quercus rubra in England (Derbyshire), and Wales (Cardiff and Barry).