Allometopon trilobellum, Owen Lonsdale, 2016

Owen Lonsdale, 2016, Revision of the genus Allometopon Kertész (Diptera: Clusiidae), Zootaxa 4106 (1), pp. 1-127 : 63

Allometopon trilobellum spec. nov.

Figs 279–283

Description. General: ( Figs 279, 280 ) Body length approximately 2.9mm. Arista sparsely short plumose. M1+2 ratio 3.0. First flagellomere slightly enlarged, subcircular. Female unknown.

Chaetotaxy: Three fronto-orbital setae with anterior seta slightly shorter. Ocellar seta 1.5 times length of tubercle. Postvertical seta very thin, as long as tubercle. Interfrontal seta minute. First flagellomere with longer margin hairs along distal and dorsal margins. Anterior dorsocentral half length of posterior dorsocentral; closely spaced posteriorly. Acrostichal seta absent. One small lateral scutellar seta.

Colour: Setae yellow. Head light yellow, whitish below frons; basal half of arista white; frons yellow with tubercle dark brown and at base of brown ill-defined V-shaped marking that encloses base of posterior two frontoorbitals; back of head with one pair of incomplete light brown stripes radiating from foramen. Scutum brown with ill-defined transition to light yellow postpronotum and notopleuron, and yellow lateral postsutural margin. Scutellum brown with yellowish spot at base of apical scutellar seta. Metanotum yellow with mediotergite and posterodorsal anepisternum brown. Pleuron and legs light yellow, becoming whitish past middle of femora. Halter light yellow. Wing slightly clouded, becoming clear along base and posterior margin. Abdominal tergites brown with lateral margin yellow, sternite 8 light brown, and epandrium, cercus and surstylus yellow.

Male terminalia: ( Figs 281–283 ) Sternites 6 and 7 not evident. Cerci nearly fused, produced into small subtriangular process. Surstylus short, narrowest at base, and apically widened with three very shallow terminal lobes, the middle of which is widest; outer surface with long distomedial setae, inner surface with cluster of small tubercle-like setae on posterior and medial lobes. Hypandrium band-like, slightly widened anteriorly, with medial seta on inner surface. Phallapodeme rod-like with narrow head, fused to hypandrium. Pregonite small, setose and fused to inner margin of hypandrium. Postgonite long, narrow, shallowly sinuate and with several inner-distal setae. Basiphallus well-developed, apparently separate from anteriorly pointed epiphallus that is fused to thickened posterior membrane. Distiphallus slightly more than 1/3 length of phallapodeme, narrow and minutely textured. Paraphallus clear, narrow and lobate with apex abruptly curved, tapered and minutely spinulose.

Etymology: The specific epithet refers to three shallow apical lobes on the surstylus.

Distribution: Papua New Guinea.

Holotype: PAPUA NEW GUINEA. East Sepik Province: Imbia, near Maprik, 19.xii.1963, D.K. McAlpine (1♂, AMSA).

Comments: Allometopon trilobellum is most readily diagnosed by a small, shallowly trilobed surstylus with a much narrowed base and tubercle-like setae on the medial and posterior lobes. The narrow, projecting cerci, pronounced postgonite, enlarged pointed epiphallus, yellow epandrium, atrophied stripes on the back of the head and yellowish spots at the base of the apical scutellars are also characteristic of the species. A number of other species in Papua New Guinea also have a wide, ill-defined stripe on the scutum, ill-defined posterolateral stripes on the frons, an entirely yellow pleuron and one pair of small lateral scutellar setae, but these belong to the A. cavernosium species group, which may be related.

Figures

FIGURES 279 – 283. Allometopon trilobellum spec. nov., holotype; 279: photo, dorsal; 280: same, lateral; 281: external genitalia, left lateral; 282: same, posterior; 283: internal genitalia, left lateral.