Diagnosis. This and the next three species are of similar size and facies to the type species of Bertula, but have more robust male genitalia with narrow, elongate valves. The female genitalia are characterised by a transverse (slightly oblique) ridge or fold of sclerotisation near the centre of the corpus bursae. Dissection is necessary to distinguish reliably between the four Bornean species, as indicated in the diagnoses of each, though this is difficult for females within each species pair recognised. The male labial palps are typical of the genus. In old specimens of momusalis the dark distal area of the forewing is relatively pale greenish brown and the postmedial boundary of the pale medial zone, also greener, is more oblique, particularly in the male, where the width is more even than in other species, though this variable. Fresh material has the medial zone of the forewing a pale greenish brown, and the basal and marginal areas are darker, somewhat greyish, with a dark edging to the latter at the postmedial. The male genitalia have the valves relatively deep as in the next species, but the left valve is less acute, the process on the centre of the ventral margin much larger than the one on the right. There is a digitate appendage at the base of the dorsal side of the uncus that is also diagnostic. The aedeagus vesica in this group has, when everted, a lateral, hammer-head appearance, the diverticulum on one side being extensively scobinate, and that extending into the ductus ejaculatorius on the other much more locally so; in momusalis there is a row of more robust teeth within the latter.
Assignation of females to males in this group has not been achieved satisfactorily. It is probable that those of momusalis are as illustrated in the plate, with rather greenish forewings that have a slightly paler and relatively broad medial band of the same colour. The specimen illustrated resembles the holotype (OUMNH). The other female illustrated is probably that of pollockisp. n., but it is likely that females of all the other three species resemble it in having a more cream-coloured medial band in a greyer surround. The undescribed species from Peninsular Malaysia (see below under lobativalvasp. n.) has female facies of this type, but its genitalia are as in momusalis. In momusalis and allies (Fig 123) the ductus bursae is sclerotised and slightly grooved and twisted along its length. The sclerotisation in the corpus bursae does not extend beyond the sclerotised fold that represents a signum and is generally transverse. The scobination in the bursa is coarser but sparser distal to the signum than it is basal to it. In females tentatively attributed to pollocki (Fig 124; slides 19727, 19731, 19738, 19812, 19915, 19916, 19960), the ductus is only very weakly sclerotised, not grooved or twisted, and shorter than in momusalis. The sclerotisation in the corpus bursae extends beyond the signum , which is more oblique. The scobination is denser in the vicinity of the signum, but does not extend much basal to it, and becomes sparser distad. The bursa is broader, more pyriform than in momusalis. The seventh segment has pouches or thickening laterally, anteriorly, possibly to engage the longer and narrower valve apices of the males.
Geographical range. Borneo, Singapore. Habitat preference. The holotype and two further specimens, one of each sex (slides: 19725, male; 19730, female), were taken by A.R. Wallace in Sarawak, probably in the lowlands. Two further females have been taken at Bidi and Busau, (slide 19742), also lowland localities in Sarawak. Two males have been taken recently in lowland forest in the Barito Ulu of Kalimantan.
