Isocossus cruciatus Holloway sp. n.
Diagnosis
♂ 20mm. The forewings are pale grey, crossed with blackish striae, heavier ones being transverse in the medial zone, slightly concave basad, and in the form of a cross in the distal third of the wing.
The male genitalia have the valve slightly constricted centrally and there is a triangular flange directed ventrally from subcostally just basal to the constriction.
Holotype ♂
SARAWAK: Gunong Mulu Nat. Park, R.G.S. Exped. 1977-8 (J.D. Holloway et al.) Site 16, March, Long Pala (Base) 70m, 324450, alluvial forest, MV on batu, BM cossid slide 82.
Geographical Range
Borneo.
Habitat Preference
The only specimen was taken in alluvial forest.
Taxonomic Notes
IsocossusRoepke**. This genus also has bipectinate antennae in the male, but the rami only have hairs irregularly distributed on the proximal side; in Paracossus there are two rows of hairs on the inner margin and two rows on the outer one in species where the antennae are bipectinate (Schoorl, 1990: 97). However, this antennal character is shared with all genera in Section 3 of Schoorl (1990: 68‑69). The condition of the fringes of the wing margins and the scaling of the labial palps seem similar to that in Paracossus (cf. p. 54), and other characters appear ambiguous across the two cladograms and amongst the definitive characters listed for each Section. The only clear distinction would therefore appear to be in the male antennae. Two of the Bornean species of Isocossus described in Part 1 have subsequently proved to be conspecific following dissection of a long series of specimens taken in Peninsular Malaysia (Dr Tan Man Wah, pers. comm.). They are I. telisai and I. seria, the former having page priority, syn. n.
Schoorl (1990: 46) noted that Cossus rufipecten Holloway had males with completely bipectinate antennae, and was unsure whether this species should be assigned to Paracossus. The original description in Part 1 compared rufipecten with vandeldeni Roepke which it resembles most closely in size and facies. Schoorl placed vandeldeni in Isocossus Roepke, its genus of original description. Yakovlev (2006) formally assigned rufipecten to Isocossus.
This raises the question of the polarity of the two antennal conditions. It is notable that Schoorl (1990) referred the Bornean species cruciatus Holloway, retak Holloway and telisai Holloway to Paracossus, whereas Yakovlev (2006) transferred these to Isocossus. They are listed under the latter here, but the situation requires further analysis on a more stringent cladistic basis.
Yakovlev (2006) described I. stroehli Yakovlev from Sumatra and Peninsular Malaysia. This appears externally to resemble rufipecten closely (see particularly fig. 68e in Part 1), butrufipecten is not mentioned in the diagnosis, nor vandeldeni Roepke, though these are listed in a short review of species constituting the genus. The male genitalia appear to be similar to those of rufipecten, so it is likely that stroehli is conspecific.
Genitalia:
