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Patchiella kolokasiaJapanese lime-taro aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same hostIdentification & DistributionLike its close relative, Patchiella reaumuri, the fundatrix of the newly described Japanese lime-taro aphid, Patchiella kolokasia, lives in a compact leaf-nest pseudogall (see first picture below). The leaf-nest is presumably also formed by twisting and stunting the epicormic shoots of Tilia species (lime).
Both images above, by permission copyright Kurosu et al. (2022), all rights reserved. The fundatrix of Patchiella kolokasia (see second picture above) is globular in shape, and coloured brick red or brown in life (cf. that of Patchiella reaumuri, which is coloured very dark green or dark brown). The fundatrix head has 5-8 wax plates dorsally. The antenna are 4-segmented; segment III is the longest, usually with an abortive division, and with 5 or 6 hairs on the basal part. The apical rostral segment has 6-10 secondary hairs. Thoracic and abdominal tergites are without wax plates, and have short sparse hairs. The cauda has more than 30 hairs. Siphunculi are absent. The offspring of the fundatrix (fundatriginiae) live with the mother in the leaf nest, and all develop to alatae. Young immatures (instars I & II) are orange pink in colour. As they mature they develop faint dark green cross bars which contrast with the orange-pink ground colour. Emigrant alatae of Patchiella kolokasia can be readily distinguished from those of Patchiella reaumuri by the wing venation. In Patchiella kolokasia the media vein of the forewing is unbranched (see first picture below) (cf. Patchiella reaumuri, which has the forewing media branched, see second picture below). Patchiella kolokasia has 6-segmented antennae, the flagellum (segments III-VI) has many hairs, segment III is longest, and the primary rhinarium on VI is large. Secondary rhinaria are transversely elongate (but sometimes irregular in shape) with dotted borders; they are distributed 8-12 on segment III, 1-3 on segment IV, 0-1 on segment V, and 0 on segment VI. The abdominal tergites have a row of weakly sclerotized plates spinally, without wax plates. The siphuncular pore is on a weakly sclerotized cone. The body length of alate Patchiella kolokasia vivipara is 2.1-3.1 mm.
Both images above, by permission copyright Kurosu et al. (2022), all rights reserved. First-instar nymphs produced by the emigrant alate on the secondary host are pale yellow. These first-instars have 4-segmented antennae and a very long rostrum. They have numerous wax plates on the head, thorax, and abdomen. The tarsi are 2-segmented with asymmetrical claws. The inner claw is longer than the outer when legs are stretched out posteriorly (see picture below) (cf. Patchiella reaumuri first instar exules, which have symmetrical claws).
Image above, by permission copyright Kurosu et al. (2022), all rights reserved. The adult aptera (see picture below) on the secondary host is pale yellow. Antennae are 5-segmented. The rostrum is long, extending beyond the hind coxae. Tergites have wax plates, which are distributed as in the first instar exule (described above). The cauda has 2 pairs of short, thin hairs. The anal plate is longer than wide. Siphunculi are absent.
Image above, by permission copyright Kurosu et al. (2022), all rights reserved. Patchiella kolokasia host alternates from lime trees (Tilia species) to the roots of taro (Colocasia esculenta). It is currently assumed that populations are holocyclic, but anholocyclic populations of Patchiella reaumuri on roots of Araceae do occur. This new species is so far only known to occur in Japan, but taro-feeding populations previously identified as Patchiella reaumuri occur in China, India, various Pacific islands, and most recently in USA. Some previous workers have suggested these were different from Patchiella reaumuri. For example Zhang (1999) described Patchiella-like aphids feeding on taro in Fujian Province, China, under the name "Gharesia kolokasia". Hence the use of that specific name for this new Patchiella species. Biology & EcologyKurosu et al. (2022) made some interesting observations on the behaviour of immature Patchiella kolokasia in the gall in relation to the fundatrix. It was shown experimentally that fundatrices of the species attract her nymphs and may become completely covered by them - but a similar sized bead placed in the leafnest attracted no aphids.
Image above, by permission copyright Kurosu et al. (2022), all rights reserved. Aphid nymphs covering their mother fundatrix is already known in Grylloprociphilus imbricator, which forms woolly colonies on twigs of beech (Fagus) trees in North America (Aoki et al., 2001). We have observed similar behaviour in Patchiella reaumuri in Britain. The reason for this behaviour in Patchiella kolokasia remains unclear. Kurosu et al. (2022) found little evidence to support the hypothesis that nymphs in the leaf nest defend the fundatrix from predators by covering her, since they showed few / inconsistent signs of attacking behavior toward introduced insects. An alternative possibility is that the fundatrix may provide some protection to the immatures when they are on top of her, but there is as yet no evidence for this. In some species of aphids, this could provide a means of moving immatures to fresh sites to establish new colonies, but this is not applicable here since all develop to alatae and depart for the secondary host. Perhaps the simplest explanation is early-instar gall-dwelling Patchiella engage in cleaning duties - as witnessed by the lack of mold or honeydew balls. Such behaviour is commonplace among gall-dwelling aphids (other than those in sealed galls) as is honeydew-repellent wax production. Whilst gall-dwelling Patchiella are variably-waxed their fundatrices, especially in Patchiella reaumuri, are less so - as is consisistent with their primary, nymph producing, role. Since Patchiella reaumuri is usually, but not always, closely ant-attended on the primary host, most of the honeydew is presumably consumed. Patchiella kolokasia are similarly waxed, no honeydew contamination is evident in their images, and Kurosu et al. do not report ants attending - making sanitation a plausible, and testable, explanation. Other aphids on the same hostPrimary hostBlackman & Eastop list 4 species of aphid as feeding on Tilia maximowicziana worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 0 as occurring in Britain (Show British list).
Secondary hostBlackman & Eastop list 12 species of aphid as feeding on taro (Colocasia esculenta) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 9 as occurring in Britain (Show British list).
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