Allometopon marginale Sasakawa, 1974

Figs 184–187

Allometopon marginalis Sasakawa 1974: 157 .

Allometopon marginale . Pitkin & Evenhuis 1989: 535 [catalogue, Australasia/Pacific].

Description. General: (Figs 184, 185) Body length 3.5mm. Antennae past pedicel missing. M1+2 ratio 3.7.

Chaetotaxy: Anterior fronto-orbital approximately 3/5 length of posterior two fronto-orbitals. Ocellar seta well-developed. Postvertical seta absent. Interfrontal seta minute. Anterior dorsocentral less than half length of posterior seta; closely spaced posteriorly. Acrostichal seta absent. Two small pairs of lateral scutellar setae.

Colour—male: Setae yellow to brownish, darker on abdomen. Frons brown around base of vertical setae and with one pair of dark brown stripes laterally (not reaching eye margin) that widen posteriorly to reach ocellar tubercle; frons adjoining stripes widely orangish; back of head with one pair of brown stripes radiating from foramen that are broadly joined basally; remainder of head light yellow; gena and anterior region of postgena silvery tomentose. Notum brown with lateral margin of paler postpronotum light yellow, anterolateral margin of notopleuron yellow, and scutum with one pair of thin, light yellow, anteriorly incurved postsutural stripes along supra-alar rows; katatergite and anatergite yellow. Pleuron and legs light yellow. Wing clear. Halter knob brown. Male abdomen dark brown with “anterior margin of first tergite, all sternites and terminalia yellow, last two tergites pale brown” (Sasakawa, 1974).

Colour—female: As described for male except as follows: setae dark brown; stripes on frons broader, darker and nearly obliterating orange anteromedial section; occiput and postgena yellow (not whitish) with brown subovate spot posteriorly on postgena; yellow scutal stripe darker, indistinct posterior to supra-alar seta; abdomen yellow past tergite 7.

Male terminalia: (Figs 186, 187) Surstylus subcircular with dense swirl of short setae on outer surface; with long, posterobasal lobe directed inwards. Cercus short. Hypandrium (from original description) broad posterodorsally and with short row of ventromedial serrations along edge. Phallapodeme with broad, shallow apical dome with vestige of apical carina evident, and with minute spinules on ventrobasal surface. Pregonite lage, flat, lobate and with scattered setae. Postgonite well-developed with three outer setae (not evident in original figure). Distiphallus approximately half length of phallapodeme (not evident in figure). Paraphallus long, apically tapered and dorsally spinulose past base.

Female terminalia: Not examined.

Distribution: Papua New Guinea (New Britain, Manus).

Holotype: PAPUA NEW GUINEA. Bismarck Islands: New Britain, Yalom, 1000m, 14.v.1962, Noona Dan Exp. 61–62 (1♂, UZMC).

Paratype: PAPUA NEW GUINEA. Bismarck Islands: Manus, Lorengau, 18.vi.1962, Noona Dan Exp. 61–62 (1♀, UZMC).

Comments: Allometopon marginale is a dorsally dark species with a brown halter knob and one pair of narrow yellow supra-alar stripes that are incurved apically, similar to those seen in A. phenomena (Figs 212, 213), which is paler on the frons and has two pairs of vibrissae, and A. lunatum (Fig. 137), which also has a basally lobate surstylus. The basal lobe in A. marginale is larger and medially directed, however, the surstylus is broader and rounded (not apically hooked), the distiphallus is longer and the pregonite is much enlarged.