InfluentialPoints.comBiology, images, analysis, design...
| Aphids | Find them | How to ID | AphidBlog |
| InfluentialPoints.com Biology, images, analysis, design... |
|
"It has long been an axiom of mine that the little things are infinitely the most important" |
|
|
Ceratovacuna [Cerataphidini]Ceratovacuna apterae in life are yellow, brown or black, the margins with white wax cones, or the whole body densely covered in wax, sometimes with long threads. The head is fused to the pronotum, but the remaining thoracic and abdominal segments are not fused. The head has two horns, usually triangular with sharp points. The head may, or may not, have wax glands in an oval group. The antennae have four or five segments, and are 0.12-0.32 times as long as the body. The eyes are triommatidia. The apical rostral segment is 0.45-0.80 times the second hind tarsal segment. There are marginal wax glands on the thoracic and abdominal segments in most species. The siphunculi are located on segment V, and have a colourless or brown ring around the pore which is elevated slightly above the surface. The cauda is transversely elongate, and has a knob with constriction, and 10-19 hairs. The anal plate is bilobed. The alate Ceratovacuna has a black head and thorax, with a yellowish, brown or black abdomen. The head has two frontal horns. The antennae have 5 (or 4-5) segments and are 0.20-0.41 times body length. Annular secondary rhinaria are distributed 16-35 on antennal segment III, 5-15 on segment IV, and 2-14 on segment V. The apical rostral segment is 0.49-0.85 times the second hind tarsal segment. Eyes are compound. The forewing media vein is once branched, and the hind wing has two oblique veins. Siphunculi and cauda are similar to those in aptera. Ceratovacuna comprises about 20 species of aphids. They are thought to host alternate between Styrax and grasses (Poaceae), although this has only been confirmed for two species (Ceratovacuna orientalis, Ceratovacuna nekoashi), and many populations may be anholocyclic. The genus is closely related to Astegopteryx. Most species form dense colonies on the undersides of leaves of bamboos or large grasses. The apterae are small to medium-sized, yellow to brown in colour and secrete much wax. Some species have horned first instar soldiers as in Pseudoregma. They are found in east and south-east Asia. Ceratovacuna nekoashi (Cat's paw gall aphid) East Asia, possibly IndiaFundatrices of Ceratovacuna nekoashi hatch in spring and transform a lateral bud of a developing shoot of the deciduous snowbell Styrax japonicus into what is known in Japan as a "cat's-paw" gall (see first picture below). These multiple-cavity galls have also been described as 'banana-bunch shaped'. The fundatrix is followed by one or two generations of apterous adults in the gall. Some of their offspring grow into second-instar sterile soldiers that play a defensive role. From July onward, emigrant alatae develop in the gall.
The alate Ceratovacuna nekoashi (see second picture below) has rather long antennae. Antennal segment III is shorter than segments IV+V, and there are 24-25 secondary rhinaria on segment III, 12-15 on segment IV and 9-13 on segment V (cf. Tuberaphis owadai, which has 0-5 rhinaria on V; Tuberaphis takenouchi, which has 0-2 rhinaria on V; and Ceratovacuna japonica, which has 4-7 on V). The front ocellus is much smaller than the dorsal ones, and is borne on a small protuberance. The rostrum reaches beyond the front coxae. The wing veins are normal, with the second oblique (= Cu1a) very slightly stouter than the first oblique (= Cu1b) vein. There are dark sclerotized cross-bands on abdominal tergites VI-VIII. The siphunculi are small, and not surrounded with hairs.
First & third images above copyright Aoki & Kurosu (2010), second image copyright Seoul National University; Emigrant alatae of Ceratovacuna nekoashi fly to the grass Microstegium vimineum, their secondary host,
and give birth to first-instar offspring on the undersides of its leaves. The nymphs and adults of the secondary-host generation (see third picture above) are reddish brown (cf. Ceratovacuna oplismeni, which are blackish purple, and Ceratovacuna subtropicana, which are yellowish orange). They are densely covered in white wax wool, and with a marginal fringe of wax tufts. They are characterized by a pair of frontal horns which have their apices somewhat curved distally; the horns are 96-140 μm long, slightly constricted at the base and 2.5-3.5 times their basal widths. The apical antennal segment of the first instar is 0.81-0.94 times the second segment of the fore tarsus (cf. Ceratovacuna orientalis and Ceratovacuna subtropicana, where that relationship is 1.00-1.10 and 0.75-0.89 respectively). The first instars are without siphuncular pores. In October, sexuparae develop on the Microstegium and fly back to Styrax japonicus. The sexuparae of Ceratovacuna nekoashi differ from the spring emigrants by having frontal horns, and less sclerotisation of abdominal tergite VI than alatae from galls. They deposit tiny first-instar sexuales (males and oviparous females) on the undersides of snowbell leaves. The sexuales move to branches without moulting and mature in the fissures of bark without feeding. There they copulate, and females each lay a single egg that overwinters. Note that Microstegium vimineum is an annual grass, so in temperate Asia no aphids can persist on this secondary host during winter. Its host alternation is therefore considered obligate. Secondary host populations are recorded from Japan, Taiwan, and Korea; the records from Uttar Pradesh (India) from the grasses Apluda mutica and Arthraxon sp. need confirmation.
|
