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Aphididae : Eriosomatinae : Pemphigini : Prociphilus
 

 

Genus Prociphilus

Leaf nest-conifer root aphids

On this page: Prociphilus bumeliae and Prociphilus fraxini caryae fraxinifolii osmanthae pini tessellatus

Prociphilus [Pemphigini]

Prociphilus species range from rather small to very large aphids. They are characterised by lacking siphunculi and having well developed wax glands, even in fundatrices.

The Prociphilus genus contains about 50 species, which are fairly evenly distributed through the northern hemisphere. Prociphilus have lost their evolutionary constraint to Populus and transferred their sexual generation in relatively recent times to live in pseudogalls on various more advanced primary hosts in, for example, the Rosaceae, Caprifoliaceae and Oleaceae. However, as in the related genus Pachypappa, the parthenogenetic generations have retained an association with the roots of conifers.

 

Prociphilus bumeliae and Prociphilus fraxini (Ash-conifer root aphids)

In spring the fundatrices of Prociphilus bumeliae and Prociphilus fraxini are brown, covered with white wax wool, and form loose leaf-nests on their primary host, usually ash (Fraxinus species). The first image below shows a mature colony. Prociphilus bumeliae and Prociphilus fraxini both have distinct wax glands on the head and thorax, as well as large, albeit indistinct wax glands on the abdomen. The 5-segmented antennae are about a third of the length of the body. There are no siphunculi.

Guest images copyright Dr László Érsek, all rights reserved.

Alates (see second picture above) have a blackish-brown head and thorax, and a light brown or yellowish red abdomen, more or less covered with white wax wool. The 6-segmented antennae are about half the length of the body.

Prociphilus bumeliae and Prociphilus fraxini can only be distinguished at the alate stage produced in the leaf nest.

  • In the Prociphilus bumeliae alate the third antennal segment is more than five times longer than the second antennal segment. Also the head has only a pair of posterior dorsal wax pore plates which are conspicuous as clearly defined pale areas much larger than the ocelli.

  • In the Prociphilus fraxini alate the third antennal segment is usually less than five times longer than the second antennal segment. The posterior wax pore plates on the head are ill-defined, but there is usually a pair of small clear anterior wax pore plates.

Both these Prociphilus species host alternate from ash (Fraxinus) to fir (Abies). Prociphilus bumeliae sometimes also uses privet (Ligustrum vulgare) or Common lilac (Syringa vulgaris) as a primary host. The fundatrices colonize the base of the primary host. Their offspring feed on the young shoots and petioles inducing the formation of leaf nests often high in the trees. These develop into alatae, which migrate to the roots of fir. In October sexuparae develop on fir, and migrate back to hawthorn where the sexual forms are produced.

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Prociphilus caryae (Apple-pine root aphid)

There are three subspecies of Prociphilus caryae, all in America. Their primary hosts are species in the apple subtribe (Malinae). In spring the fundatrix and her offspring form pseudogalls by rolling half of the leaf up on itself (see first picture below). This leaf roll is usually discoloured yellowish. In western America, Prociphilus caryae caryae gall the leaves of serviceberry (Amelanchier laevis). Again in western America, Prociphilus caryae arbutifoliae gall the leaves of toyon (Photinia arbutifolia =Heteromeles salicifolia). In eastern America Prociphilus caryae fitchii gall Saskatoon berry (Amelanchier alnifolia, see first picture below) and apples (Malus domestica, Malus angustifolia).

Images above by permission, copyright Claude Pilon, all rights reserved.

In June the offspring of the fundatrix develop wings to give the emigrant alatae (not pictured). The emigrant alate has a dark head bearing two pairs of very pale and clearly-defined wax pore plates. One pair is on the frons and the other on the vertex. Their antennae are dark with 14-22 secondary rhinaria on segment III, 1-6 on segment IV, 0-5 on segment V, and 0-1 on segment VI. Antennal segment I is shorter than its basal width. The thorax is dark with oval wax plates on the mesothorax. The wings are dusky, especially towards the distal end. The wing veins are distinctly bordered, and the forewing media vein is unbranched. The abdomen is pale with large marginal wax plates increasing in size towards the caudal end. Siphunculi are absent, and the cauda bears 2-6 hairs.

Emigrant alatae of the three subspecies can be distinguished as follows (for more details see Smith, 1969):

  • Prociphilus caryae caryae (=P. c. alnifoliae) have secondary rhinaria on antennal segments III-VI usually 18-4-1-0. The rhinaria are not in a single row, and are narrow to oval oblong, often less than 0.5 times the diameter of the segment. The head has large wax plates. Rostral segments RIV+V usually bear 2 accessory setae. The cauda has 3-7 setae.
  • Prociphilus caryae arbutifoliae have secondary rhinaria on segments III-VI, usually 26-7-3-0. The rhinaria are variable, some are narrow, some oblong and relatively broad. RIV+V has 2-6 accessory setae. Denticulation is sparse on rhinaria of antennal segment III. The cauda bears 3-7 setae. The body length of emigrant alatae of ssp. arbutifoliae is 2.9-4.1 mm.
  • Prociphilus caryae fitchii (=P. c. pyri) have secondary rhinaria on segments III-VI (18-4-3-0). The rhinaria are denticulate, in a single row, and usually longer than the segment diameter. There are two pairs of distinct wax plates on head. RIV+V has 4 accessory setae, the cauda has 2-6 setae. The body length of emigrant alatae of ssp. fitchii is 1.8-3.3 mm.

Emigrant alatae of subspecies fitchii and subspecies caryae migrate to secondary hosts, the roots of pine (Pinus species). Alatae of subspecies arbutifoliae migrate to an unknown secondary host, probably pine roots. Through the summer the aphid populations on the roots of their secondary host are tended by ants. In October-November sexuparae develop, and these return to the primary hosts where they deposit sexuales in bark crevices near the base of the tree or in nearby leaf litter. Instead of host-alternating, some parthenogenetic populations persist throughout the year on pine roots. Prociphilus caryae fitchii is widely distributed in eastern North America.

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Prociphilus fraxinifolii (Leafcurl ash root aphid)

Overwintering eggs of Prociphilus fraxinifolii hatch in April-May on ash (Fraxinus) before bud burst. The newly-emerged fundatrices feed on the buds. As leaves develop, these aphids begin to feed at leaf bases and stalks and bracts; as a result, leaves become gradually deformed until they are tightly curled and clumped to form 'leaf nests' (see first picture below). They are sometimes also discoloured to a red-brown colour. Inside the pseudogall feeds a colony of fundatrigeniae (see second picture below). Early-instar immature Prociphilus fraxinifolii are pale yellow, but later instar immatures and adults are a pale yellowish green (see third picture below). Many aphids are thickly coated in wax, secreted by large wax glands on the head and in three rows on the body. The wax has to be resecreted after each moult so recently moulted aphids have little wax. A crucial role of the secreted wax is to prevent these aphids becoming contaminated by their own honeydew (see second picture below of wax-coated honeydew droplets) and that of other members of the colony (see also for Eriosoma lanigerum).

Images above by permission, copyright Claude Pilon, all rights reserved.

The generation of fundatrigeniae includes both apterous and alate morphs (see pictures below). Characteristics of the alate can be used for identification purposes. Alatae of Prociphilus fraxinifolii have a yellow-green abdomen (cf. Prociphilus fraxini and Prociphilus bumeliae on ash, which are brown with green patches.) The base of antennal segment VI bears 1-5 irregularly-shaped secondary rhinaria, differing from those on antennal segment III (cf. Prociphilus fraxini and Prociphilus bumeliae on ash, which have no secondary rhinaria on the base of antennal segment VI).

On the roots there is a symbiotic association betweeen the aphid and the fungus Boletrinellus merulioides. When feeding on the roots, Prociphilus fraxinifolii is enlosed by hollow structures (sclerotia) of the fungus. It has been suggested that in exchange for housing the aphid, the fungus receives nutrients excreted by the aphid in its honeydew. In autumn these root colonies produce alate sexuparae which return to the surface, and give birth to males and oviparous females, thus completing the annual life cycle. Remaining leafnest colonies also produce sexuparae in the autumn. Aphids which remain on the roots may reproduce parthenogenetically all-year-round on Fraxinus roots.

Prociphilus fraxinifolii is common and widely distributed in the USA, and is also found in Canada and Mexico. It has been introduced to Chile, South Africa and Europe, from where it has spread to Iran and Kazakhstan. It has also recently been reported from Beijing, China.

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Prociphilus osmanthae (Osmanthus gall aphid)

Prociphilus osmanthae live in curled-leaf pseudogalls on Osmanthus. The leaves are rolled downwards at right angles to their midribs (see first picture below). Like other species of the genus, Prociphilus osmanthae has well developed wax gland plates on the back of the head, thorax and abdomen which secrete white wax fibres. The wax covers both immature and adult aphids and the interior of the pseudogalls.

The adult apterae (see second picture below) have the head, thorax, antennae and legs dark gray and the abdomen greyish-green. The antennae are 5-segmented, shorter than the body, with the terminal process short, 0.19-0.23 times as long as segment V. The apical rostral segment (RIV+V) is 0.61-0.86 times the length of the second hind tarsal segment (HTII). The siphunculi are very small, reduced almost to a pore. The cauda is broadly rounded. The mean body length of adult apterae is 1.77 mm.

Images above copyright Dr László Érsek, all rights reserved.

Alatae of Prociphilus osmanthae (not pictured) developing in spring colonies on Osmanthus spp. have a wax-covered olive-green abdomen. Their wings are infuscated along the costal margin and at the base and the forewing veins are narrowly dark-bordered. There are 27-31 secondary rhinaria on segment III, 9-12, on segment IV, 8-12 on segment V and 0 on segment VI. The body length of alatae is reported to be 3.3-4.0 mm.

In their native Japan Prociphilus osmanthae migrate in late May from Osmanthus (Osmanthus spp.) to an unknown secondary host. The species is found in Japan, and is also reported to occur in Meghalaya, India. Prociphilus osmanthae has recently been introduced to Hungary where these photos were taken.

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Prociphilus pini (Hawthorn-pine root aphid)

Overwintering eggs on hawthorn hatch in spring to give fundatrices which , together with their progeny, curl and yellow hawthorn (Crataegus) leaves. The progeny all develop to alates, which have a light green to greyish green abdomen (see pictures below). These migrate to the secondary host, the roots of Scots Pine (Pinus sylvestris) and related Pinus species.

Guest images copyright Alan Watson Featherstone all rights reserved.

The adult apterae of Prociphilus pini on the secondary host are cream or pale pinkish and are covered with dense wax wool. In October winged sexuparae (see pictures above) develop on the pine roots and migrate back to hawthorn. The head has paired wax gland plates showing as clear areas between antennae and/or on the posterior part of head. The number of secondary rhinaria on the antennae is diagnostic - segment III: 15-32, IV: 5-12; V: 2-11; VI: 0. The body length of the sexupara is 1.6-2.3 mm.

Sexuparae are produced on pine roots in October, but British populations seem to mainly persist throughout the winter on pine, and it is less commonly found on its primary hosts, hawthorn. Prociphilus pini occurs in the British Isles, and in north-west and central Europe.

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Prociphilus tessellatus (Woolly alder aphid)

The eggs which the woolly alder aphid host lays on its primary host, silver maple, hatch in spring to give the fundatrices. The first picture below shows the resultant colonies on silver maple (Acer saccharinum). The offspring of the fundatrices are winged, and they migrate to their secondary host, alder, where they form colonies along the branches (see second picture below).

Adult apterae of Prociphilus tessellatus are quite large brownish aphids which are covered with a thick layer of white woolly wax. Their antennae, legs, anal plate and subgenital plate are all brown to black, and the wax pore plates are pigmented (cf. Prociphilus baicalensis which has the antennae, legs, anal plate and subgenital plate of aptera all lightly pigmented, and the wax pore plates are pale). The apical segment of the rostrum (R IV+V) is longer than the second hind tarsal segment (HT II), and R IV bears 4-10 accessory hairs (cf. Prociphilus mexicanus where R IV+V is shorter than HT II, and R IV bears 2-3 accessory hairs).

First image above copyright Jim Baker, North Carolina State University, Bugwood.org, Creative Commons license
Second image above copyright Lynette Elliott, third image copyright Stan Gilliam, both under a Creative Commons license.

The colonies of Prociphilus tessellatus on alder grow and persist through the summer (see first picture below). Then, in autumn, alate sexuparae develop (see third picture above). They are also thickly covered in white woolly wax, and have narrow, transverse secondary rhinaria on the antennae, including 1-5 on the base of antennal segment VI (cf. the alate sexupara of Prociphilus mexicanus which has the secondary rhinaria on antennae more oval, and they absent from the base of antennal segment VI).

The woolly alder aphid (Prociphilus tessellatus) should really be known as the 'woolly silver maple-alder aphid', given it host alternates between silver maple (Acer saccharinum, its primary host) and alder (Alnus, its secondary host). Alate sexuparae (see fourth picture above) fly from alder to silver maple in autumn, where they produce a sexual generation. After mating the oviparae lay eggs which overwinter. Not all the aphids migrate from alder - some do not mate, but overwinter as parthenogenetic apterae under fallen leaves or in loose earth beneath alder trees. The woolly alder aphid is found widely in North America, but has not so far been recorded in Europe or Asia.

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Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). 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.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.