Aphid Biology and Morphology (Hemiptera: Aphidomorpha)

Below we summarise the biology and external morphology of insects loosely-described as aphids, known colloquially as 'plant lice' (USA) or greenfly/blackfly (UK). Aphids in the broad sense are in the infraorder Aphidomorpha, which comprises 5218 living species and 314 extinct ones. They are in the suborder Sternorrhyncha along with 3 other superfamilies: Aleyrodoidea (white flies) which has more than 1500 species, Coccoidea (scale insects and mealy bugs) with about 8000 species and Psylloidea (jumping plant lice) which has over 3000 species worldwide. Using the classification of Remaudière & Remaudière (1997), ignoring extinct taxa, the Aphidomorpha contains one superfamily (the Aphidoidea) which contains all the extant species of aphids divided between 3 families: the Adelgidae, Phylloxeridae and Aphididae (or 'true aphids'). Characteristics of those three families are given below.

Aphids are sap-feeding, soft-bodied insects that often have multiple morphs, are variably waxed, and undergo cyclical parthenogenesis. Aphididae are almost exclusively phloem-feeders, the remainder mainly take parenchyma cell-sap. The beak-like rostrum enclosing their piercing mouthparts emerges from beneath the head. Siphunculi are peculiar to Aphididae and a few extinct taxa - as is, except for the Phylloxeridae, the cauda. The tarsi are normally 2-segmented, and claws paired. The wings are paired, membranous, and generally clear - but wingless forms are common. The forewings have thickened, often fused, anterior veins and reduced posterior ones. The hindwings are considerably smaller (in fossil taxa sometimes reduced to halteres). Wing venation details help distinguish higher taxa and older fossils, but is otherwise of limited use. Early instars, and some apterae, resemble other Sternorrhyncha nymphs.

Early Aphidomorph fore-wing (~249.5 Ma). Copyright Szwedo & Nel, Acta Palaeontol. Pol. under a Creative Commons License.

Unidentified Aphidomorpha aptera (40-50 Ma). Image Anders L. Damgaard via Wikimedia Commons, CC BY-SA 4.0.

Have about 51 species in 2 genera (Adelges, Pineus), on conifers (Pinaceae), and are native to Northern Hemisphere boreal and temperate zones. Introduced to the southern hemisphere, some are invasive pests. Their life cycles are variable, complex, and comprise multiple morphs. They typically alternate between a primary spruce (Picea sp.) host and a secondary coniferous host of another genus. Alternation takes 2 or more years, but some are single-host. Reproduction is entirely oviparous.

Only dispersive parthenogenetic adults are winged. All morphs produce wax. Apterous parthenogenetic females are covered in flocculent wax. Many species have a highly glandular body surface. Alatae have a distinct head, thorax and abdomen; 5 antennal segments, of which III, IV and V each have a single (often large) sensorium. They have compound eyes plus 3 ocelli. Plates on the prothorax and abdominal segments are variously fused and faceted according to species. The wings are held roof-like over the abdomen at rest. The forewing has 3 oblique veins arising from the subcostal vein; the cubitus veins are separate at their bases; the media is unbranched; there is no separate radial sector. The hindwing has 1 oblique vein - the media. There are 4 or pairs of abdominal spiracles. First instar nymphs having longer legs and antennae, are the only mobile apterous forms. They have small, three-segmented, antennae; typically with a long segment III with a long apical seta. Their eyes are reduced to three ocelli. The head, thorax and abdomen are fused to an oval shape. The dorsal surfaces have a series of segmental sclerites bearing wax glands. Sexual forms have 4-segmented antennae, have a rostrum, and wingless (winged in fossil spp.). The female copulatory organs formed into a reversed, tripartite ovipositor.

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Pineus pinifolii fore wing (notation amended). Image after Vickery, R.A. (1908).

Pineus orientalis, gallicola.

A small family of perhaps 83 species in 8 genera in 2 subfamilies, mostly on Juglandaceae or Fagaceae. Many species form galls on hickory (Carya) species, some host alternate. Reproduction is entirely oviparous.

The aptera body is pear shaped, nearly semi globular with a flat underside, and normally narrowing towards the end. Wax, if present, not flocculent. The antennae are short, with only 3 segments; the terminal process process is little developed or non-existent. The rostrum is short. Apterae only have triommatidia but alatae have a pair of compound eyes. The wings of the alate are held flat in repose. The fore wing is without a radial sector, the media is unbranched, and the anal and cubital veins arise on a common stalk. The hind wing is without oblique veins. Most Palaearctic species have spiracles on abdominal tergites I-V, but the mainly Nearctic species only have them on abdominal tergite I. Siphuncular pores are absent. There is no ovipositor except in Acanthochermes. The sexuales are apterous and dwarfish, the sexual female lays one egg of about the same size as itself.

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Phylloxera glabra forewing (notation amended). Image after Vickery, R.A. (1908).

Phylloxera glabra, adult viviparous female with eggs.

The 'true aphids', Aphididae (sensu Remaudière), has more than 5000 living species in 510 genera divided among 24 subfamilies. They consume phloem sap from leaves, stems and roots of woody and herbaceous vascular plants (angiosperms, conifers, bryophytes) especially Compositae, conifers, Rosaceae, grasses and willows. Most species are restricted to closely related hosts, but 10% alternate between herbaceous species and a perennial host where they may reproduce sexually. Some are ant-dependent, albeit variably. Whilst primarily temperate, species have been described from every non-polar land mass, a few are cosmopolitan. Most species are harmless, others are notorious pests.

Adults may be winged, often seasonally, but are commonly wingless. They have a pear shaped body of variable colour, often greenish or greyish, very roughly 2 mm long. Multiple morphs, waxing, and neoteny are common. Adult antennae are generally 6-segmented, variably tapering, often on tuberculi. Their eyes are usually compound with an ocular tubercle. Both sexes generally have mouthparts. The rostrum is normally 4 segmented which at rest is usually held beneath the body. Wings are usually held 'tent-like' over the abdomen when at rest. Most have a cauda, and siphunculi, albeit their dimensions vary; never an ovipositor. Males are commonly winged; females are commonly wingless. Sexual reproduction is oviparous, asexual is viviparous.

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Aphis fabae, forewing, dorsal, SEM. Copyright Franielczyk-Pietyra & Wegierek, Zoomorphology under a CC4 licence.

Aphis fabae adult aptera & nymphs.

A small subfamily, with only 14 recognised species all in genus Aiceona. They feed mainly on laurels (Lauraceae). Unlike most aphids, sexuales may be found in colonies at almost any time of year, and the oviparae lay stalked eggs. All species live in east, south and south-east Asia.

In apterae the antennae are usually 6-segmented, with a short terminal process. The compound eyes are only 3-faceted. The body is not sclerotized over the dorsum and bears no marginal tubercles. The siphunculi are well developed on hair-bearing cones. The cauda is broadly round at the apex. In alatae the pterostigma of the forewing is short, with fine hairs along the subcostal vein and pterostigma. Both oviparae and males are alate. The males often lack siphunculi.

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Aiceona titabarensis aptera, mount. By permission of Roger Blackman, copyright AWP all rights reserved.

A small but distinctive and widespread subfamily with about 24 species in one genus. Some species host alternate from dogwood (Cornus) to the roots of grasses; others live year round on the roots of grasses or sedges. Alate sexuparae of host-alternating species deposit small, yellow-brown sexual morphs on dogwood leaves in autumn. They have a Holarctic distribution through North America, Europe and eastern Asia.

Adult apterae are medium-sized greenish grey or grey often with a sclerotic dorsal abdominal plate. The antennae are rather short, with a short terminal process.The eyes are large with ocular tubercles. There are round, flat marginal tubercles on the prothorax and most abdominal segments I-VII. The siphunculi are round or pore-like, on low hair-bearing cones. The cauda is broadly semi-lunar. The forewings of alatae have a characteristic large, but truncated and dark pterostigma.

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Anoecia corni, winged sexupara (autumn migrant) and immature sexuales.

This largest Aphididae subfamily has at least 2483 species in 256 genera in 2 tribes: the Aphidini and the Macrosiphini. The former-subfamily Pterocommatinae is now included as a subtribe (Pterocommina) within the Macrosiphini. Most Aphidinae live on angiosperms, with a few on conifers and ferns. Some species host alternate between a woody perennial primary host where sexual reproduction occurs, and one or more herbaceous secondary hosts. Alate viviparae migrate to the secondary hosts in spring and early summer, and alate sexuparae and male migrants return to the primary host. Most aphid pests on crops and ornamental plants are Aphidinae, and some of these are among the most polyphagous. Members of the Aphidinae occur in nearly every region of the world, but particularly in the Holarctic and oriental regions.

The antennae of apterae are long and usually 6-segmented, with a terminal process which is markedly longer than base. The compound eyes are always multi-facetted, and usually have a triommatidion in the ocular tubercle. The rostrum usually has segments IV and V fused into a single compact apical segment. Marginal and/or spinal tubercles may be present on the prothorax and the abdominal segments. Siphunculi are most commonly elongate cylindrical, but are otherwise very variable in shape. They are very rarely stump-shaped or absent. The anal plate is never bilobed or emarginate (=narrow notch at tip) and the cauda is usually tongue-shaped, or short and broad, but never knobbed. Alatae have secondary rhinaria present on antennal segment III and often also on IV and V. The wings in alate morphs are usually held in a tent-like posture over the back.

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Aphidini : Aphis sambuci, adult aptera & nymphs.

Macrosiphini : Macrosiphum euphorbiae, green form, aptera.

The Baltichaitophorinae has only one extant species, Parachaitophorus spiraeae. It lives on Spiraea spp. forming compact ant-attended colonies on stems and the bases of young offshoots. Its life cycle is unknown, but it is thought to host alternate. Sexuales have been found on Spiraea cantoniensis in autumn. They are found in Japan, Korea and east Siberia.

Apterae have reduced eyes with only triommatidia in nymphs, fundatrices and oviparae. They have very long dorsal hairs arising from dark tuberculate bases. The siphunculi are low and truncate and the anal plate is emarginate (=narrow notch at tip). In the alate the secondary rhinaria are roundish, placed on small tubercles. The pterostigma is rather long, and the hind wing is reduced, with only one oblique vein. The body of the alate is covered with numerous long hairs.

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Parachaitophorus spiraeae aptera, mount. Image via HUSCAP, copyright Shun'ichiro Sugimoto

The second largest subfamily with more than 400 species in about 80 genera, in 8 tribes (Calaphidini and Panaphidini). Most feed on woody angiosperms especially birches (Betulaceae), beeches (Fagaceae), and elms (Ulmaceae), although some species feed on herbaceous plants. They are not usually attended by ants. Many economically important pests belong to this subfamily with some of these being invasive. They mostly have a Holarctic distribution.

In most genera all viviparae are alate. The antennae are frequently longer than the body. The antennal terminal process is at least one half length of the base of last segment. An ocular tubercle is usually present on the compound eye. The body dorsum sometimes has capitate setae and spinal tubercles may be present on some segments. The siphunculi are usually short, stump-shaped or pore-like, situated on abdominal tergite VI or between V and VI. The anal plate is usually bilobed and the cauda is knobbed, bluntly triangular or broadly rounded. The alatae have secondary rhinaria present on antennal segment III and often also on segments IV and V. The radial sector on the wing is often reduced or missing.

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Euceraphis punctipennis, fundatrigenia.

The Chaitophorinae has 163 species in 11 genera in 2 tribes: the Chaitophorini and the Siphini. Most Chaitophorini feed on woody angiosperms especially in the willow (Salicaceae) and maple (Aceraceae) families. The hosts of the Siphini are mainly grasses (Poaceae), but some feed on sedges (Cyperaceae) or rushes (Juncaceae). There is no host alternation. The predominant morph is the apterous viviparous female with alatae produced in variable numbers. The colour ranges from whitish to green and brownish to black and the dorsum is never wax-covered. Species in the Chaitophorini are often attended by ants. Species in both tribes have a Holarctic distribution.

The adult viviparae have antennae shorter than the body with 4, 5 or 6 segments. The dorsal cuticle is often sclerotic with or without dark pigmentation, and sometimes also rugose or spinulose. The body usually has numerous long hairs, which may be pointed, blunt, spatulate or furcate. In the Chaitophorini the siphunculi are usually truncate conical or stump-shaped, whilst in Siphini they are reduced to rim-like structures. The cauda varies from broadly crescent-shaped to distinctly elongate with an apical knob. The anal plate is never deeply cleft or bilobed. Chaitophorinae alatae at rest hold their wings vertical. The wings are normal, to rather long and narrow. The forewing has the media either once- or twice-branched. Wing venation is sometimes brown-shadowed.

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Chaitophorus populeti adult aptera.

A rather small subfamily with 40 species in 5 genera. There is no host alternation and all species feed on members of the maple (Aceraceae) family. They are active, rather robust aphids which often have specialised parasitoids. They have a Holarctic distribution with one genus Drepanosiphoniella that is only found at high altitudes.

All viviparae are alate. Secondary rhinaria are in a row on the basal part of antennal segment III. The body dorsum sometimes has capitate hairs, but never stellate or mushroom-shaped ones. Marginal tubercles are absent on the pronotum and the tergites. In the alate morph the fore femora are almost always adapted for jumping, enlarged or swollen with tibial bases shovel-like. The siphunculi are tubular, much longer than wide, often very long, narrowing towards the apices. The cauda is knobbed and the anal plate is slightly emarginate (=narrow notch at tip) or bilobed. Oviparae often have the posterior abdomen protruding.

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Drepanosiphum aceris, alate.

The Eriosomatinae has 301 species in 48 genera and 3 tribes (Eriosomatini, Fordini, Pemphigini). They typically host alternate between trees especially elms (Ulmaceae) and poplars (Populus) and the roots of herbaceous plants. The spring generations induce characteristic galls or pseudogalls on the primary host. Alate spring migrants leave the galls to colonise the secondary host. The alatae that make the autumn migration back to the primary host are sexuparae, producing both males and oviparous sexual females. The sexual morphs are apterous and dwarfish; they reach maturity very quickly without feeding. After mating the dwarf ovipara lays a single egg. Many species may continue parthenogenetic reproduction on the secondary host roots through the winter if mild. Eriosomatini and Pemphigini are Holarctic, the Fordini are mostly Mediterranean & east Asian with a few American species.

Apterae and nymphs generally have only triommatidia but no compound eyes, with the border between the head and pronotum normally distinct. The antennae are short, with a very short terminal process. Siphunculi are present only as pores or are absent. They have a broad, rounded cauda which is not constricted, and the anal plate is entire. Wax glands are often well developed, usually in groups of plates producing fibrous or filamentous wax. Alatae usually have transversely oval or annular secondary rhinaria which are not confined to antennal segment III. The media vein of the forewing is never twice-branched, but has only one fork or is unbranched.

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Pemphigus bursarius, alate.

A subfamily with 150 species in 16 genera and 3 tribes (Cervaphidini, Greenideini, Schoutedenii). They are found on the leaves and shoots of dicotyledonous trees and shrubs with no host alternation. They are sometimes attended by ants. The season for production of sexuales is variable, and the oviparae of some species lay stalked eggs. Some species are considered pests. They are confined to Southeast Asia and adjacent countries.

The terminal process of the antennae is often shorter than the base of the last segment. Apterae of Schoutedenii and Cervaphidini only have triommatidia as eyes, but Greenideini have compound eyes. The distal segments of the rostrum (RIV & V) are not fused. In some genera the seventh abdominal tergite bears a pair of projections about as long as antennal segment IV. The siphunculi are either short and conical, of medium length or very long, often curved outwards and bearing many hairs. The cauda is usually either broadly rounded or triangular, never tongue-shaped or knobbed. The anus is usually surrounded by an apparently wax-secreting area.

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Greenidea ficicola aptera. Copyright Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org under a Creative Commons Attribution 3.0 License.

The subfamily has 181 species in 44 genera and 3 tribes (Cerataphidini, Hormaphidini, Nipponaphidini). In the tropics and subtropics they have complex two year life cycles involving often elaborate galls (see picture below) on their primary hosts which are various tree genera, such as witch hazels (Distylium, Hamamelis) and snowbells (Styrax). Host alternation of most Hormaphidinae species is by alate sexuparae in autumn. Members of this subfamily occur predominantly in East and South-East Asia, with a few in Europe.

Most species are highly polymorphic, and the secondary host generations are often sedentary and coccid- or aleyrodid- like. They have short appendages concealed beneath the body and glands that secrete wax. Apterae and young nymphs have triommatidia, but no compound eyes. The antennae have 3-5 segments, and are much shorter than the body. The terminal process is shorter than the base of the last antennal segment. Spinal and marginal tubercles are absent. The tarsi have two long capitate dorsoapical hairs. The siphunculi may be present as pores or be absent. The cauda is knobbed or rounded, and the anal plate is bilobed. Some Hormaphidinae alatae hold their wings flat at rest. The antennae of alatae bears narrow, ringlike secondary rhinaria.

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Hormaphis hamamelidis alate by permission, copyright Claude Pilon, all rights reserved.

A very small subfamily of grass-feeding aphids with only 4 species in 1 genus (Israelaphis). Their unusual life cycle is related to the Mediterranean climate. The parthenogenetic phase exploits short-lived annual grasses following autumnal rains. Sexuales are produced and diapausing eggs laid in spring. They are only found in the Mediterranean region and western Iberia.

The apterae are green to yellow. The antennae have an elongate terminal process, evenly tapering from the base to the apex of the last segment. There are secondary rhinaria on antennal segment III in the aptera. In the aptera the dorsum is armoured, with nodulose or wrinkled sculpturing. Spinal setae of tergite VIII are mostly on a pair of horn-like processes. Siphunculi are swollen in the middle. The knob of the cauda is egg-shaped and the anal plate is bilobed. The alate morph is extremely rare. Wing venation is abnormal with a pointed, elongate pterostigma. Large sclerites are developed on the ventral side of the abdomen. In life there is sometimes slight whitish waxy powdering.

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Israelaphis carmini. Reproduced by permission, copyright Daniel Rojas via biodiversidadvirtual.org, all rights reserved.

One of the larger subfamilies with 346 species in 19 genera in 5 tribes (Eulachnini, Lachnini, Stomaphidini, Tramini, Tuberolachnini). There is no host alternation, and in the largest tribe, Eulachnini, most species spend their entire lives feeding on conifers. All other Lachninae are associated with angiosperms, living on oaks & beeches (Fagaceae) or woody roses (Rosaceae), or on roots of herbaceous plants. The Lachnini & Eulachnini are Holarctic, the Tramini are Palaearctic.

Lachninae are mostly large aphids, often strongly pigmented and covered with hairs. The antennae have a short terminal process. The rostrum is usually long, and segments IV and V are not fused. The dorsal abdomen does not have an extensive solid black patch, and marginal and spinal tubercles are absent. Wax glands are not arranged into facets. The siphunculi are usually pore-shaped and set on low cones - or in some Tramini, completely absent. The cauda is short and broadly rounded. On alatae the secondary rhinaria are more or less round, and the pterostigma is not very dark and much longer than wide.

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Cinara laricis, aptera & nymphs.

A small subfamily of 24 species in 3 genera (Ceriferella, Lizerius, Paoliella). In life these aphids are covered with waxy pulverulence, or fluffy wax secretions. They feed on members of the laurel (Lauraceae) and other plant families, and are restricted to South America.

The terminal process of their antennae is often elongate, narrowed from its base onward. The rostral apical segment is often strongly sclerified. The body bears up to 12 pairs of long finger-like processes. The fore-femora are mostly enlarged and adapted for jumping. The second tarsal segment has very long ventral setae. The siphunculi on tergite V are little raised above the surface. The cauda is long, finger-like, and knobbed. In the alate the mesoscutellum often bears setae. The fore wings mostly have a long, pointed pterostigma and the radial sector is almost straight. Body processes are less developed or absent in alatae. In a few species blister-like adhesive vesicles occur on the ventral posterior abdomen of the ovipara.

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Paoliella nirmalae aptera. By permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka.

A small subfamily of 6 species in 1 genus (Macropodaphis). These aphids are weakly wax-powdered; there are also short white stalks of wax secreted from the dorsal body glands. Most species feed on cinquefoils (Potentilla spp.). Life cycles are unknown. They are found in the steppe zones of Central Asia (central & eastern Palaearctic).

The clypeus is greatly enlarged. The eyes are compound, with the ocular tubercle distinct, but small. The antennal terminal process tapers evenly from base to apex. The dorsum has transverse rows of numerous tubercular processes bearing hairs and wax glands. The fore femora are much enlarged and adapted for jumping. The siphunculi are short, cylindrical, without a flange. The cauda is knobbed and the anal plate indented.

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Macropodaphis paradoxa aptera, mount. By permission of Roger Blackman, copyright AWP all rights reserved.

A small subfamily with nine or more species in one genus (Mindarus). They are all conifer-feeding, mainly on species of fir (Abies) or spruce (Picea). The fundatrices produce the sexuparae the same year just after bud break, as the new needles begin to expand. These aphids are covered in waxy secretions and feed on the current-year needles which can cause appreciable damage to tree foliage. Four species are found in the Nearctic and four or more in the Palaearctic.

The eyes in early larval stages, and often also of the adult aptera, consist only of a triommatidium. The rostrum is retractable into the long first segment and last two segments are fused. They have well-developed wax glands. The siphunculi are reduced to small siphuncular pores sited on cones or are absent. The cauda of the aptera is very small and crescent-shaped. The Mindarinae alate has the pterostigma in the fore wing pointed and extending to the very apex of the wing. The cauda in the alate morph is triangular and the anal plate is sclerotic. Both oviparae and males are apterous, and are mostly very small.

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Mindarus abietinus, adult aptera.

A small subfamily of 18 species in 1 genus (Neophyllaphis). They feed without host alternation on conifer species in the podocarp (Podocarpaceae) and monkey puzzle tree (Araucariaciae) families. Aphids may be covered in life with waxy pulverulence. Sexual morphs occur in mixed colonies with parthenogenetic morphs in spring, summer or autumn. Several species have winged oviparae. They are found in the southern hemisphere and mountains of the tropics, extending northward into China and Japan. Some species have been introduced into North America and Europe.

The antennae are shorter than body, and with a short terminal process. In the aptera the eye is usually only a triommatidium. Frontal and abdominal tubercles are absent. Wax gland fields around the dorsal body setae are mostly developed as scattered pits or small cribriform discs. The siphunculi on abdominal segment VI are porelike and may be elevated, with or without setae at the base. The cauda has a more or less elongate knob. In alatae the secondary rhinaria are often annular but do not encircle the entire segment. The alatae have compound eyes with triommatidia in ocular tubercles. In oviparae the anal segment is modified bearing a large knobbed or rounded cauda covered with wax gland pores.

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Neophyllaphis varicolor colony. Copyright Perry Babin under a Creative Commons Attribution License.

The Phloeomyzinae appears to comprise a single, somewhat variable, species (Phloeomyzus passerinii) in 1 genus. The aphids live on bark and in crevices on trunks of poplar trees (Populus spp.). The apterae are green, covered with dirty white wax wool. There is no host alternation, and the only alatae are sexuales. Oviparae and males are produced in September-October in the northern hemisphere. After mating the oviparae each lay just two eggs. Anholocyclic overwintering by apterous viviparae is also common. Phloeomyzus passerinii is found in Europe, north Africa, parts of Asia and South and North America.

The parthenogenetic forms are all apterous and are without compound eyes - they have only triommatidia. The antennae have the terminal process shorter than the base. Secondary rhinaria are absent from all morphs. Wax glands form large faceted plates on abdominal segment VII. The siphunculi are slightly elevated pores and the cauda semicircular. The wings of the sexual alatae are held flat at rest. The sexuales - both males and oviparae - are alate.

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Phloeomyzinae passerinii aptera, mount. By permission of Roger Blackman, copyright AWP all rights reserved.

The subfamily Phyllaphidinae has 15 species in 4 genera. They mainly feed on oaks and beeches (Fagaceae), but species of one genus Machilaphis are found on laurels (Lauraceae). Alatae and apterae are usually heavily waxed. They have a Holarctic distribution, with the range of two species also extending further south.

The eye of the apterous morph is made up of one ventral and one dorsal group of facets, without a triommatidium. Antennal segment II is often longer than the first, and the terminal process is much shorter than the base. The first tarsal segments are without dorsal setae. The suture between femur and trochanter is often lacking in the apterous morph. There are extended fields of wax gland pore elements on the dorsal sclerites and on legs and antennae. The siphunculi are pore-like and located on tergite VI and the cauda is rounded. In the alate morph the ocular tubercle is weakly developed or absent. Oviparae mostly have perforated subsiphuncular wax gland plates. In the alate morph the cauda is sometimes knobbed.

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Phyllaphis fagi, alatae.

A small subfamily with 5 species in 2 genera (Neoantalus, Pterasthenia). The legs and sometimes also the antennae are covered with fluffy wax secretions or waxy powdering; the aptera sometimes has stalk-like secretions on the dorsum. Both genera are mainly associated with woody plants in the Fabaceae (= Leguminosae). Little is known of their biology but some are thought to reproduce parthenogenetically all year. They are found in sub-Saharan Africa.

In apterae the eyes are compound with triommatidia, and the head and pronotum are generally separated. There are small antennal tubercles and the antennae have a very long terminal process. The fore-femora are enlarged and adapted for jumping. There are no processes on the dorsum, but the dorsal body setae are sometimes accompanied by small cribriform wax gland discs. The siphunculi are cone-shaped or rarely pore-like. The knob of the cauda is egg-shaped or tapers to a slender point and the anal plate is bilobed. In the alate morph the pterostigma is truncate or pointed at apex. Neoantalus alatae have secondary rhinaria on antennal segments III-VI. The hind wing is reduced in size, with or without an oblique vein.

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Pterasthenia albata aptera, mount. By permission of Roger Blackman, copyright AWP all rights reserved.

There are 55 species in 12 genera in 2 tribes (Saltusaphidini, Thripsaphidini). They are almost entirely associated with the Cyperaceae. Most species have some waxy powdering, and some genera have flocculent waxy secretions. All of the species are monoecious and holocyclic. The group is a present throughout Europe and North America. Two species occur widely throughout the Holarctic region, at least 26 species are restricted to the Palaearctic Region and 19 are restricted to the Nearctic region.

Body form is usually elongate; if oval there are distinctive black dorsal markings and femora are enlarged for jumping. The triommatidium is within the compound eye and there is no ocular tubercle. Antennae are shorter than the body. The legs may be normal, or modified for jumping. The empodial setae are mostly fan-shaped, but sometimes hair-like. Dorsal body setae are numerous, often modified to become fan-shaped or mushroom-shaped. The siphunculi are pore-like or short cylindrical. The cauda has a squarish knob and anal plate is bilobed. In many species alatae are quite rare. The wings are often somewhat elongate. The oviparae and males are apterous, the latter dwarfish.

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Subsaltusaphis picta, aptera. By permission, copyright Thomas Legrand, all rights reserved.

A small subfamily with 13 species in 2 genera (Neosensoriaphis, Neuquenaphis). All species in the subfamily feed on southern beeches (Nothofagus). There is often some waxy powder on the body. All species are monoecious holocyclic with alate males and apterous oviparae. They are restricted to South America, with most species found in Chile.

Antennae are mostly very elongate with the terminal process narrowed from its base to the apex. Dorsal abdominal setae are arranged as distinct rows and are mostly on finger-like processes of various lengths. The siphunculi on tergite V are densely reticulated at the apex. The knob of the cauda is spherical to turnip-shaped and the anal plate is bilobate or incised. In alates the fore wings are normal. The fore femora are almost always enlarged and adapted for jumping. The dorsal processes in the alate morph are usually much smaller than in the apterae.

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Neuquenaphis sensoriata aptera, mount. By permission of Roger Blackman, copyright AWP all rights reserved.

A small subfamily of aphids, with 14 species in 2 closely related genera (Taiwanaphis, Sensoriaphis). Taiwanaphis species feed on trees, especially in the myrtle family (Myrtaceae). Most of the species in genus Sensoriaphis feed on southern beech (Nothofagus). Sexual forms occur throughout the year. The body in life is without noticeable waxy powdering. Some Sensoriaphis species are ant attended (see picture). Taiwanaphis spp. occur in India and east and south-east Asia, whilst Sensoriaphis spp. are found in Papua New Guinea, Australia and New Zealand.

In apterae the eyes are compound, and the triommatidium is well developed. The fore femora are not adapted for jumping. The dorsum of the body has no processes close to the midline, but there are often short finger-like processes marginally on some or most tergites. Stigmatic plates of the abdomen are often shifted to the ventral side of the abdomen. The short stump-shaped siphunculi are on tergite V and are densely striate. The knob of the cauda is egg-shaped or turnip-shaped. The anal plate is bilobate or incised. In alatae on the anterior margin of the pronotum there is a flat wart on each side bearing the anterior marginal seta. The oviparae are apterous and have two pairs of densely striate subsiphuncular wax gland plates. The subgenital plate is large, with over 100 setae.

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Sensoriaphis nothofagi aptera. By permission, copyright Nicholas A. Martin, Plant & Food Research, all rights reserved.

The subfamily Tamaliinae has 5 species in 1 genus (Tamalia). They live in galls on manzanitas and bearberries (Arctostaphylos). Unlike other gall producing aphids, Tamalia are monophagous rather than host alternating. In Tamalia coweni, not only the fundatrix, but also later generations of wingless females are capable of inducing galls. Winged females disperse to other sites suitable for gall induction and deposit wingless gall-forming females. The subfamily is restricted to North America.

On the aptera the eyes are reduced to a prominent triommatidian ocular tubercle. Antennae are short with 4, 5 or 6 segments, and have numerous spicules. Both dorsal and ventral sides of the body are covered with spicules and numerous long sharp bristles. Sclerification and pigmentation is variable dorsally, sometimes with broad bands. The legs are short. The siphunculi are absent, or as pores on small cones. and the cauda is rounded. The alate has compound eyes with a protruding ocular tubercle. The antennae are 6-segmented, with a short apically rounded terminal process. The abdomen is decorated with many bristles, and the cauda is rounded. Tamalia oviparae are winged and have a pair of large ventral wax plates on tergites VI and VII.

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Tamalia coweni aptera. Copyright James Bailey under a Creative Commons Attribution 2.0 Generic license.

The subfamily Thelaxinae has 18 species in 4 genera (Glyphina, Kurisakia, Neothelaxes, Thelaxes). They mostly feed on oaks (Fagaceae), birches and alders (Betulaceae). There is no host alternation and all species are holocyclic. In some species immature sexual forms are produced in early summer, but then aestivate until autumn when mating takes place, and eggs are laid. All species are ant-attended. All species are Holarctic.

Apterae of Thelaxinae have eyes of only three facets (triommatidia) and no distinct line of demarcation between head and thorax. The 5-segmented antennae have a short antennal terminal process. The dorsum has extensive sclerotisation, which is sometimes segmentally divided. There are no wax glands. The siphunculi are rather large pores placed on low cones. The cauda is either broadly rounded or knobbed and the anal plate is rounded. Alatae have antennae with a few secondary rhinaria on antennal segment III. The forewing media is a once-branched. Wings are held flat at rest, and the forewings have a thick scaly band along most of the front edge of the wing.

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Thelaxes dryophila, colony attended by Formica rufa.