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Hormaphidinae : Cerataphidini : Ceratovacuna nekoashi
 

 

Ceratovacuna nekoashi

Cat's paw gall aphid

On this page: Identification & Distribution Other aphids on the same host

Identification & Distribution

Fundatrices 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 (see second picture below).

The alate Ceratovacuna nekoashi 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.

Note: There are four closely related species in the nekoashi group (Ceratovacuna nekoashi, Ceratovacuna oplismeni, Ceratovacuna orientalis and Ceratovacuna subtropicana). These different species cannot be distinguished morphologically on the primary host, but they can be discriminated on the secondary host (see below, & in more detail in Aoki et al., 2013, who initially characterised the four species by analysis of mitochondrial RNA sequences).

First image above copyright Aoki & Kurosu (2010), second image copyright Seoul National University,
both under a creative commons licence.

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 picture below) 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.

Image above copyright Aoki & Kurosu (2010) under a creative commons licence.

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.

 

Other aphids on the same host

Primary host

The Ceratovacuna nekoashi species group has been recorded from 4 snowbell species (Styrax formosanus, Styrax japonicus, Styrax obassia, Styrax suberifolius) but Aoki et al. (2013) only found Ceratovacuna nekoashi on 2 of them (Styrax japonicus, Styrax obassia).

Secondary host(s)

The Ceratovacuna nekoashi species group has been recorded from at least 9 secondary host species in the Poaceae (Apluda mutica, Arthraxon hispidus, Chloris virgata, Digitaria sanguinalis, Imperata cylindrica, Indocalamus sp., Microstegium vimineum, Muhlenbergia japonica, Phragmites australis and possibly Oplismenus compositus, Oplismenus undulatifolius, Sasa senanensis, Sasa veitchii plus an Arthraxon sp.). Aoki et al. (2013) only found it on one of these (Microstegium vimineum) and suggest the others should be treated as misidentifications until shown otherwise.

Acknowledgements

We are grateful to Utako Kurosu & Shigeyuki Aoki for providing images from Aoki & Kurosu (2010) for this page.

We have used the keys and species accounts of Takahashi (1936) (as Astegopteryx nekoashi), Aoki & Kurosu (2010) & Aoki et al. (2013) together with those of Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections 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

  • Aoki, S. & Kurosu, U. (2010). A review of the biology of Cerataphidini (Hemiptera, Aphididae, Hormaphidinae), focusing mainly on their life cycles, gall formation, and soldiers. Psyche 2010, Article ID 380381, 34 pp. Full text

  • Aoki, S. et al. (2013). The aphid Ceratovacuna nekoashi (Hemiptera: Aphididae: Hormaphidinae) and its allied species in Korea, Japan and Taiwan. Entomological Science 16, 203-221. Abstract

  • Takahashi, R. (1936). Aphids of the genus Astegopteryx Karsch, with descriptions of new species from Sumatra and Formosa (Aphididae, Hemiptera). Proc. R., Ent. Soc. Lond. (B) 5(5), 96-102.