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Hormaphidinae : Nipponaphidini : Thoracaphis kashifolia
 

 

Identification & Distribution

Thoracaphis kashifolia form colonies on the upper surfaces of leaves of Quercus glauca in Japan and Taiwan. The apterous adults of Thoracaphis kashifolia (see first picture below) are aleyrodiform (immature whitefly-shaped), sessile, flattened, black, strongly sclerotized on the dorsum (especially on a broad marginal area) and covered with wax powder. They are found throughout the year on the leaves. The second picture below shows an immature Thoracaphis kashifolia.

Note: Thoracaphis kashifolia = Thoracaphis kashifoliae = Thoracaphis kashiwae = Astegopteryx kashifolia = Xenothoracaphis kashiwae.

Both images above copyright Kurosu et al. (2016) under a Creative Commons Attribution License.

A clarified mount of Thoracaphis kashifolia is shown in the first picture below; its head is to the right. The antennae are pale, very short and 3-segmented. The apical rostral segment is somehat longer than wide. The prosoma (which comprises the head, thorax and abdominal segment I) makes up 80% of the body length. It is almost smooth, with a pair of longitudinal folds and short dorsal setae. The legs are pale and short, with the hind legs rather slender - the distribution of the legs shows the extent of the prosoma. The fused abdominal segments II-VII are completely separated from the prosoma and bear 6 pairs of short submarginal setae, a few submedian setae, but no postero-mesial setae on VII. The siphunculi are minute and pore-like. The first tarsal segments have 3,3,2 setae (on fore, mid & hind legs). The globular cauda is at least as long as wide and bears 8 very long hairs. The anal plate is pale with about 6 very long hairs on each lobe. The genital plate is pale with 12 long hairs at the hind margin. The body length of adult Thoracaphis kashifolia apterae is about 1.5 mm.

Both images above copyright Kurosu et al. (2016) under a Creative Commons Attribution License.

Thoracaphis kashifolia colonies produce alatae in autumn. Colonies producing alatae become covered with candy floss-like wax (see second picture below) during this period. The alate vivipara of Thoracaphis kashifolia (not pictured) is black, with the fore wings blackish along the subcosta; wing veins and pterostigma are black. The antennae are rather stout, stouter than tibiae; secondary rhinaria are distributed 14-15 on III, 7- 8 on IV, and 4-5 on V. The abdomen is without sclerites on the dorsum. Tergites VII and VIII bear 4 moderate hairs, and the 2 median hairs on tergite VIII are rather closely placed. The siphunculi are small. The cauda is pale, slightly constricted basally, nearly as long as wide - there are some long hairs, with the pair at the apex longer than the cauda. The anal plate is pale, divided with each lobe much larger than cauda.

Thoracaphis kashifolia lives on the upper sides of leaves of Ara-kashi (=Japanese blue oak, Quercus glauca), and possibly Aka gashi (=Japanese evergreen oak, Quercus acuta) in Japan. (Uye, 1924, described this species based on specimens collected from Quercus acuta, but no other aphidologist has found it on that host.) Thorocaphis spp. are now only known from anholocyclic populations producing parthenogenetic generations on what were the original secondary hosts (Quercus, Lindera). Alatae appear in November together with defensive nymphs (see below). Thoracaphis kashifolia is found in Japan and Taiwan.

 

Biology & Ecology

Production of defensive nymphs

Kurosu et al. (2016) made the first discovery of defensive individuals on their secondary hosts amongst the Nipponaphidini. They found that soldier-caste differentiation occured in the alate generation of Thoracaphis kashifolia. First-instars in woolly colonies had their fore- and mid-legs enlarged to a varying extent with large, strongly curved claws. First-instar nymphs produced early in the season (destined to become alates - see first picture below) had fore-femoro-trochanters shorter than those produced later (the defensive nymphs - see second picture below). The moulting rate (assessed as the percentage of 'pharate' individuals: those that have completed metamophosis to the next stage but have yet to moult) of defensive-nymphs was very low (less than 5% to zero), suggesting they are semi-sterile.

Both images above copyright Kurosu et al. (2016) under a Creative Commons Attribution License.

These semi-sterile forms were produced by apterae from early September onward, and were shown to act as defenders of the colony. When a moth larva was introduced to the colony, the defensive nymphs grasped the moth larva with their enlarged fore- and mid-legs (see picture below) - but normal non-defensive nymphs also joined in on attacking the moth larvae.

Image above copyright Kurosu et al. (2016) under a Creative Commons Attribution License.

In addition to grasping it with their legs, defensive nymphs inserted their stylets deep in the body of the lepidopteran larva to which they were clinging. Such deep insertion of stylets has not been observed with defensive nymphs of other groups. Aphids of the tribe Nipponaphidini on the secondary host have stylets - far longer than the rostrum, rather like adelgids. When not extended, their stylets are kept coiled in the head. Kurosu et al. (ibid) surmised that defensive nymphs of Thoracaphis kashifolia may employ stylets inserted in the body of an enemy as an anchor, so as not to be detached easily from it.

Another peculiar feature of the first instar nymph of Thoracaphis kashifolia is its eyes, each of which consists of three facets (triommatidia). In all first-instar nymphs of Thoracaphis kashifolia one facet is located apart from the remaining two, on the underside of the head and directed downward. The same type of triommatidia are known in the first-instar nymphs of Metathoracaphis isensis, which also form colonies on the upper sides of leaves of their host oak (Quercus gilva). Kurosu et al. (2016) suggest that such triommatidia may be an adaptation in the life on the upper side of a leaf, and that the downward-directed facets might enable the nymphs living on the upper side to perceive enemies on the underside through the leaf tissue.

 

Other aphids on the same host

Blackman & Eastop list 30 species of aphid as feeding on Ara kashi, Japanese oak (Quercus glauca) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none occurring in Britain (Show British list).

Blackman & Eastop list 10 species of aphid as feeding on Aka kashi, Japanese evergreen oak (Quercus acuta) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists none occurring in Britain (Show British list).

Acknowledgements

We are grateful to Utako Kurosu and Prof. Shigeyuki Aoki for permitting us to use their images of Thoracaphis kashifolia on this page - and to Aoki for his helpful comments.

We have used the keys and species accounts of Takahashi (1958) and Ghosh & Raychaudhuri (1973) (both as Xenothoracaphis kashiwae), and Kurosu et al. (2016) together with those of Roger Blackman & Victor Eastop (as Thoracaphis kashifoliae) 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

  • Kuruso, U. et al. (2016). Defensive nymphs of the woolly aphid Thoracaphis kashifolia (Hemiptera) on the oak Quercus glauca. Psyche, Article ID 4036571, 11 pp Full text

  • Ghosh, A.K. & Raychaudhuri, D.N. (1973). Studies of the aphids (Homoptera: Aphididae) from Eastern India XV. A study of Nipponaphis Pergande and related genera with descriptions of a new genus and eight new species. Kontyu 41(4), 477-496 Full text

  • Takahashi, R. (1958). Three new genera of Aphididae from Japan (Homoptera). Kontyu 26(4), 181-186.

  • Uye, Tenji. (1924). Notes on three species of Pemphigidae from Kyushu. Insect World 28(1):14.