Bocana erythusalis Walker, [1859] 1858, List Specimens lepid. Insects Colln Br. Mus., 16: 177, partim (see below).
Hydrillodes gravatalis
Figure 175Figure 193
Diagnosis. This and the next species, erythusalis Walker, have very similar facies but differ in genitalia features. Sexual dimorphism of wing facies is not marked on the upperside. Males also have dense scaling on the labial palps, that of the second segment black, broadly spoonlike, within which nestles the paler, straw-coloured apical part of the third segment; this is often flexed backwards to make contact with the similarly coloured frons of the head. The facies of both species is also similar, the forewings blackish brown with straw-white, punctate submarginals and a similarly coloured zone between the discal lunule and the postmedial, this pale area somewhat broader in erythusalis, which is also slightly larger. Identification is best confirmed from the genitalia where males have the dorsal process of the valve with the apex rounded dorsally, curving round to a point ventrally, whereas in erythusalis it is angular dorsally and ventrally, with the dorsal angle slightly more produced. The female genitalia of the two species are very similar, with the ostium set in a deep pocket, flanked by small lobes only. The ductus bursae is slender. In erythusalis (slide 10816; females tentatively assigned, as discussed under that species) the ductus is one fifth longer than in gravatalis, and the corpus bursae is about one third larger.
Geographical range. Indian Subregion to Sundaland.
Habitat preference. Most material taken in recent surveys is from the lowlands to the lower montane zone at around 1000m, where the species may be slightly commoner. Records from above this at 1780-1790m on G. Mulu were confused with those of the next species.
Biology. The species has been reared from larvae feeding on detritus and pericarp of Shorea and Dipterocarpus (Dipterocarpaceae) (Robinson et al., 2001).
