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Thoracaphis scale aphidsOn this page: Thoracaphis kashifolia linderae
Thoracaphis have aleurodiform (= whitefly-shaped) apterae with very short 3-segmented antennae, 0.06-0.08 times the body length. The head is without horns, and the eyes are triommatidia. The apical rostral segment is 1.10-1.18 times the second hind tarsal segment. The prosoma (=head+thorax) is completely separated, or somewhat incompletely separated, from the fused abdominal segments II-VII. The fused abdominal segments have 6 pairs of submarginal hairs. Tergite VIII has 2-4 hairs. First tarsal segments have three hairs, of which middle one is stout and spiny. The siphunculi are pore-like. The cauda is broader than long and the anal plate is bilobed. Alatae have 5-segmented antennae with annular secondary rhinaria. The forewings have the media vein once branched and the hind wings have both obliques.
There are currently six described species in the genus Thoracaphis, and several recorded, but undescribed. More have been described in the past, but many of these have been moved to other genera. Blackman notes that what remains can hardly be said to form a homogeneous group. It is thought they were associated in the past with Distylium (Hamamelidaceae) as primary host, as are other Nipponaphidini, but the species described are now only known from parthenogenetic generations on what were the original secondary hosts. All species are found in parts of East and South Asia.
Thoracaphis kashifolia (Woolly oak scale aphid) Japan, Taiwan
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. A clarified mount of Thoracaphis kashifolia is shown in the second picture below; its head is to the right. The antennae are pale, very short and 3-segmented. The apical rostral segment is somewhat 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.) Thoracaphis 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.
Thoracaphis linderae (Wax-crusted scale aphid) Japan
Adult apterae of Thoracaphis linderae (see first picture below) are aleyrodiform, flattened and broadly oval, with a dorsum coloured green or reddish-brown, becoming sooty black with age. Published descriptions do not mention wax production, but there appear to be 3 sets of marginal wax gland plates on each side of the cephalothorax. In old specimens wax may completely cover the dorsum. The head is fused with the thorax to give the cephalothorax (= prosoma), which comprises the anterior 80% of body length. Their eyes are 3-faceted and marginal. The 3-segmented antennae are submarginal, on the underside, shorter than the distance between themselves, reaching the level of the eyes, and nearly as long as hind tibia. The rostrum is short, the apical rostral segment a little longer than segment III, much longer than the tarsus, tapering, about 1.7 times as long as wide. There are many small papillae densely scattered over cephalothorax, and 6 long thick-based (prosomal) hairs on each side arising from the submarginal area of the underside. The much-reduced abdomen is short, comprising only about 20% of the body length. It is fused with, and sunken into, the cephalothorax, with the anterior part having 5 faint traces of segmentation and some small papillae. There are also 6 lateral abdominal submarginal hairs on each side, but only the anterior one is long and visible. The siphunculi are very small, visible as small pores on tergite V. The cauda is pale, short, constricted basally, almost straight at the hind margin, with some long hairs. The anal plate is pale, divided, with some very long hairs on each lobe. The subgenital plate is pale, much larger than anal plate, with about 25 long hairs along the hind margin. The body length of adult Thoracaphis linderae apterae is 1.8-2.0 mm.
Images above by permission, copyright Akihide Koguchi, all rights reserved.
Whilst Thoracaphis linderae alatae have been recorded (Shinji, 1926), we are unable to find a description of this morph. Immature Thoracaphis linderae (see second picture above) have the anterior dorsum rather more strongly sclerotized than other parts. Numerous long wax tendrils arise from the margin of their cephalothorax and abdomen.
Thoracaphis linderae feeds on the twigs and stems of Lindera species, a shrub in the Lauraceae. Alatae have been collected in May. The life cycle is uncertain. Most Thoracaphis species are thought to have had winter hazel (Distylium) as their primary host in the past, but are now only known from parthenogenetic generations on the secondary host. Shinji (1926) found presumed fundatrices on Lindera, but Aoki (pers. comm.) notes these may merely be apterous adults. Thoracaphis linderae is only known to occur in Japan.