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Hydrillodes Guenee

Type species: lentalis Guenee, India.

Synonyms: Bibacta Moore (type species truncata Moore, India); Cellacrinata Bethune-Baker (type species grisea Bethune-Baker, New Guinea); Echana Walker (type species abavalis Walker, Sri Lanka); Olybama Walker (type species thelephusalis Walker, South Africa = uliginosalis Guenee); Ragana Swinhoe (type species gravatalis Walker, Sri Lanka).

This genus is particularly distinctive and well-defined. Males of many (but not the type) species have a conspicuous scaled flap folded over the forewing costa, seen only elsewhere in Globosusa Swinhoe; this is probably a homoplasious development, as Globosusa otherwise shares features with Alelimma Hampson (p. 63). This flap has beneath it a brush of pale hairs, variable in colour. On the underside the structure apears as a blister bounded by an arcuate groove. The forewing venation has M2, M3 and CuA1 arising from a long stalk, and the male forewing flap, when present, causes distortion amongst the radial sector veins; see illustrations by Owada in Inoue et al. (1982: plate 383, figs 4-12). The labial palps are variable in development and can be prominently scaled and recurved in males though never extending beyond the patagia. The male antennae are ciliate to fasciculate. The forewings are usually grey to dark blackish brown, with a paler, often reddish, medial zone defined by irregular, transverse antemedial and postmedial fasciae. This medial zone often contains a relatively basal dark discal lunule. There may also be a punctate white submarginal fascia. The hindwings are generally greyer and often paler than the forewings, and usually also have an obscurely darker discal lunule.

In the male abdomen the eighth segment is unmodified, though the sternite is shallow with a slightly concave distal margin that is fringed with hair-scales. In the genitalia, the valves are usually broad and deeply bifid, the arms tapering, slender. The aedeagus vesica is generally but variably scobinate, the coarseness of this tending to be stronger more distally. There are often also several robust cornuti near the base of the vesica.

The female genitalia have been mentioned on p. 17 as showing extreme development of the coiling of the ductus seminalis, this being closely spiralled with many turns, and based on a sclerotised zone in the wall of the bursa. There are two prominent signa, scobinate plates, in the centre or distal part of the bursa. There are also complex processes directed posteriorly from the sterigma, possibly to receive the cleft valves of the male.

The species may be separated into three groups, but it is possible that the first is paraphyletic in relation to the remaining two, and the third may be nested within the second.

Males of the first group lack a forewing flap (but may have a fold), and the facies is similar to that of the female. The male labial palps in a few species are densely scaled. The male genitalia have the valves more shallowly cleft than in the other groups, with the apices of the dorsal (many species) and ventral parts (almost always) tending to be rounded to bulbous, rugose, spiny or serrate; exceptions with more tapering but usually still serrate processes are amongst the more remote Pacific species. The aedeagus vesica is generally scobinate and is characterised by a central digitate diverticulum; large cornuti are lacking. Females have a narrow ductus bursae. This group includes several very widespread species (see also below).

The second group includes most of those where the males have a prominent flap on the upperside of the forewing costa (pacifica Owada and funeralis Warren (Owada, 1987) have this feature vestigial or lacking), but the labial palps are not strongly modified by dense scaling. In the male genitalia, the ventral margin of the tegumen is convex, serrate or with fewer spines, these not being adjacent to the uncus (see the next group). The valves are more deeply cleft than in the first group, the two processes tapering, acute. The aedeagus vesica lacks a digitate diverticulum, but usually has several cornuti basally, some with multiple spines; scobination may be stronger on one or more lobes in the centre of the distal part. Females of this and the next group have a broad ductus bursae. The group includes four new related species that are currently only known from Borneo.

The third group includes a few montane Sundanian species and also has males with a costal flap on the forewing, but this is joined by a brush of scales or hairs on the costa adjacent to it basad; these may extend round the margin of the flap also, and are set somewhat obliquely to the costa. In the male genitalia, the ventral margin of the tegumen has an acute spine immediately adjacent to the uncus. The valves are deeply cleft, the dorsal process long, slender, sinuous, with subsidiary spines; the ventral process is also curved, tapering, and may be slightly sinuous. The aedeagus vesica is similar to that of the second group, but the cornuti are always single spines, two at the base and sometimes one distally.

The larva of the type species is described below. Those of all species probably feed on dead foliage. The author (Holloway, 1979: 532) inadvertently established a large culture of the New Caledonian species in bracken fern (Pteridium), gathered when fresh, used to stuff a mattress. Most other records noted for individual species below are also of plant detritus.

The genus extends throughout the Old World tropics and subtropics to Japan and Australia, with the first group of species mentioned above extending from Africa through to Polynesia (Holloway, 1983), with a number of species restricted to Pacific island groups, including several in Tahiti (Orhant, 2003). Species of the genus were not quantified in the survey of G. Kinabalu (Holloway, 1970, 1976), but were abundant in montane samples.

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