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Horned aphidsOn this page: Genus Astegopteryx bambusae formosana
Aphids in the genus Astegopteryx host alternate between Styrax as the primary host, and palms and bamboos as the secondary hosts. They make a variety of elaborate galls on the primary host. As is often the case with gall makers, the morphs which are found within the galls often differ greatly from the morphs of the same species on the secondary host.
Apterous morphs in the galls are usually wax-covered in life. The head is without horns and has 4-8 spines anteriorly and ventrally. The antennae have 4-5 segments and are 0.16-0.26 times as long as the body. The eyes are triommatidia. The apical rostral segment is 0.83-1.00 times as long as the second hind tarsal segment. The prothorax is fused to the head. The (fore, mid, hind) first tarsal segments have 3-4, 3-4, 2-3 hairs. The abdomen has linear S-shaped wax glands on segments I-VI or VII. The cauda is transversely elongate, with or without an indistinct constriction.
The emigrant alate vivipara from the gall has the head without horns, but with 6-15 small hairs in two areas dorsal and lateral to the median ocellus, or 32-40 small hairs also present in the median area. The antennae have 5 segments, and are 1.4-1.9 times as long as the body. Antennal segments III-V bear ring-shaped annular secondary rhinaria. The apical rostral segment is 0.73-0.96 times as long as the second hind tarsal segment. The media vein of the forewing is once branched, and the hind wing has 2 oblique veins. Wings are held horizontal at rest (hence the name Astegopteryx). Abdominal segments I-V are colourless, but segments VI-VII sometimes have pale brown patches. Siphunculi are on segment VI, and cauda is transversely elongate.
Apterae of Astegopteryx on the secondary host in life are yellow or whitish grey with a pattern of green (or orange, red or violet). They have a wax fringe along the body margin, and sometimes wax bands on the dorsum, or the dorsum is completely covered with wax. The head dorsally has 2 horns with 4-12 hairs, with the tips pointed or rounded. Antennae have 4-5 segments, and are 0.15-0.31 times the body length. Eyes are triommatidia. The apical rostral segment is 0.52-0.92 times the second hind tarsal segment. The prothorax is fused to the head, and the body has a furrow posterior to pronotum. The first tarsal segments have 2-4, 2-4, 2-3 hairs (fore, mid, hind). The siphunculi are cone-shaped, colourless or brown. The cauda is transversely elongate with a knob and constriction. Wax gland groups may occur on each segment of the body.
There are about 24 Astegopteryx species. For several (many?) species either the primary or secondary hosts are unknown. Some species are undoubtedly holocyclic in parts of their distribution. For species where both hosts are known, they host alternate between Styrax where they are gall-forming, and monocots, specifically palms and bamboos. They are found in East, South and Southeast Asia.
Astegopteryx bambusae (Bamboo horned aphid) East & Southeast Asia
Alate Astegopteryx bambusae sexuparae fly to leaves of snowbell (Styrax suberifolius) in spring (not autumn) and deposit sexuales on leaf undersides. The first-instar sexuales soon leave the leaves and hide in narrow spaces such as in unfolding buds of the host tree. They mature and copulate, and females each lay a single egg. First instar fundatrices soon hatch from the eggs and induce galls on stems of developing Styrax suberifolius shoots. The galls (see first picture below) comprise about 20 elongate subgalls radiating out from one point on the stem. These galls may be modified by invading Ceratoglyphina bambusae (Kurosu & Aoki, 1990). After one or two generations of apterous adults in the galls, emigrant alatae are produced over a period of several months. Migratory alate Astegopteryx bambusae from their primary host have 18-19 annular secondary rhinaria on antennal segment III, 6-7 secondary rhinaria on segment IV, and 4-7 on segment V (Tao, 1961, as Astegopteryx sasakii). These migrate to the secondary host, bamboos.
Astegopteryx bambucifoliae has now been synonomized with Astegopteryx bambusae.
First image above by permission, copyright Aoki & Kurosu, all rights reserved
The apterae of Astegopteryx bambusae on bamboo are broadly pear-shaped and coloured yellow to pale green. They vary in markings, with one form (formerly called A. bambusifoliae) having two dark green uninterrupted longitudinal stripes on a yellow background (see second picture above). Alternatively they may have two separate pairs of short green stripes (see third picture above). Wax is sometimes present as a fringe at the margin of head and usually in tufts around the thorax and abdomen. The antennae of the aptera are 0.22 times as long as body, with a terminal process that is 0.22 times as long as the base of the antennal segment VI. The apical rostral segment (RIV+V) is about as long as the second hind tarsal segment (HTII), but sometimes a little shorter. The siphunculi are on dark sclerotic cones, bearing thick 7-9 hairs. The cauda is broader than long, and bears 6 hairs. All the pictures above show yellow (rather than pale green) forms, but pale green forms are similarly common. The alate viviparae from the secondary host has 28-39 annular secondary rhinaria on antennal segment III, 10-17 secondary rhinaria on segment IV, and 9-17 on segment V (Noordam, 1991).
Host-alternation is known to occur in Taiwan between Styrax suberifolius and various bamboos. Styrax suberifolius is distributed through southern China, Myanmar, Vietnam and Taiwan, and it seems likely that host alternation occurs wherever the primary host is available. Where it is not available (Indian subcontinent), populations are assumed to be anholocyclic on bamboo. The aphids form spaced-out colonies on the undersides of leaves, often the older leaves, of many bamboo species including Bambusa spp. and Dendrocalamus latiflorus (and possibly Phyllostachys lithophia & Phyllostachys edulis). The species is often attended by ants which forage the honeydew. Astegopteryx bambusae has a very wide distribution including the Indian subcontinent and throughout east and south-east Asia.
Astegopteryx formosana (Dark spot horned aphid) India, China, Taiwan, Indonesia, Malaysia.
Adult apterae of Astegopteryx formosana on the secondary host (primary host unknown) are very broad-bodied and pale yellow or greenish-yellow, with the head, pronotum and siphunculi brownish-orange. There is an extensive unbroken, dark blue-green patch on the dorsum (not visible in clarified mounts) which is broadest anteriorly (cf. most other Astegopteryx are with or without green, but the green is always interrupted, at least absent in the middle of abdominal segment III and IV). There is a marginal fringe of white wax on the head, and all thoracic and abdominal segments. The head bears frontal 'horns' with rounded tips. The antennae are pale and have 4, or (incompletely divided) 5 segments. The apical rostral segment (RIV+V) is 0.59-0.77 times as long as the second hind tarsal segment. The head is fused to the pronotum. The abdominal segments have almost colourless marginal and marginal sclerite wax glands. Abdominal tergite VI usually has 3 or more hairs, and tergites II-III each have 9-15 hairs in addition to those near the wax glands (cf. most other Astegopteryx, where tergite VI usually has 2 hairs, and tergites II and III each have 4-11 hairs). The legs are pale. The siphunculi are cone shaped. The cauda is transversely elongate, somewhat constricted at the base and with 7-9 hairs.
Images above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka. (accessed 12/8/20).
The alate Astegopteryx formosana has a brown head and thorax, with a yellowish green or yellow abdomen largely covered with a dark greenish-black dorsal spot. Their eyes and antennae are black, and the legs are colourless apart from the tarsi, and distal ends of the femora and tibiae. The head has very short frontal horns.
Astegopteryx formosana is found on the undersides of bamboo leaves (Bambusa, Dendrocalamus, Gigantochloa). In Taiwan this species seems to be mainly restricted to Dendrocalamus latiflorus, although it has also been found on Bambusa oldhami. Astegopteryx formosana occurs from India across to China and Taiwan and south to Indonesia and Malaysia.