Allometopon horridum, Owen Lonsdale, 2016

Owen Lonsdale, 2016, Revision of the genus Allometopon Kertész (Diptera: Clusiidae), Zootaxa 4106 (1), pp. 1-127 : 34-35

Allometopon horridum spec. nov.

Figs 113–119

Description. General: ( Figs 113, 114 ) Body length approximately 2.9mm. Arista short plumose. M1+2 ratio 4.6. First flagellomere slightly enlarged, higher than long, more strongly produced dorsally. Female unknown.

Chaetotaxy: Three fronto-orbital setae, anterior seta 2/3 length. Ocellar seta approximately 1.5times longer than tubercle. Postvertical seta minute, very thin. Interfrontal seta minute. First flagellomere along distal and anterodorsal margins with hairs longer than width of arista base. Anterior dorsocentral half length of posterior dorsocentral; closely set posteriorly. Acrostichal seta absent. One small lateral scutellar seta.

Colour: Setae yellow to brownish. Antenna yellowish-white; head yellowish-white below antenna; basal 2/3 of arista white; ocellar tubercle dark brown, connected to one pair of ill-defined, brownish to reddish lateral stripes that fade to midpoint of frons; back of head with one pair of stripes radiating from foramen that fuse basally; parafacial, gena and postgena silvery tomentose. Scutum brown with lateral margin yellow, including only notopleuron and postpronotum presuturally; darker along dorsocentral rows. Scutellum brown with yellow spot at base of apical seta. Metanotum yellow with dorsal half of anatergite and mediotergite brown. Pleuron and legs yellowish-white. Halter yellow. Wing lightly clouded, becoming clear towards posterior margin. Abdomen yellow with tergites 1–6 brown with lateral margin narrowly yellow, sternite 8 brown and epandrium brown basally.

Male terminalia: ( Figs 115–119 ) Epandrium with bare, swollen U-shaped distomedial band possibly homologous with cercus. Surstylus angled posteriorly, with slightly narrower base, and angled, truncated apex with irregular row of large, thick setae (shorter anterior setae darker); with long, narrow lobe emerging from anterobasal region of inner surface that is covered with minute tubercle-like setae; posteromedial margin with mushroomshaped lobe that supports cluster of long, dark, tubercle-like setae; outer surface bare basally and anteromedially, with single long posterobasal seta. Hypandrium band-like, dorsally fused to phallapodeme and ventrally with sheet-like extension that fuses to sternite 6; with medial cluster of 2–3 setae. Phallapodeme broad and plate-like with dome-like apical section. Pregonite irregular, confluent with hypandrium and with small ventral lobe with several setae. Postgonite long and narrow with distal section deeply bifid and apically setose. Basiphallus broad and flat, fused to small, pointed epiphallus. Distiphallus lobate, flat and membranous. Paraphallus slightly shorter than distiphallus, lobate, flat and membranous; with lightly sclerotized medial strip with several dorsoapical spinules.

Etymology: The specific epithet is from the Latin for “dreadful”, “bristly” and “rough”, describing the characteristic surstylus.

Distribution: Papua New Guinea.

Holotype: PAPUA NEW GUINEA. Oro Province: Kovelo, near Kokoda, 6.i.1964, D.K. McAlpine (1♂, AMSA).

Comments: The male terminalia of Allometopon horridum are most diagnostic, especially the complex, internally spinulose (setae colour heterogeneous) surstylus that includes an inner anterobasal lobe and a medial mushroom-shaped posteromedial process beaing numerous stout spines. The distiphallus and paraphallus are reduced, smooth and lobate, the phallapodeme is broadly dome-like and the postgonite is apically bifurcated. Externally, the scutum is yellow with a broad ill-defined medial stripe, the scutellum is brown with yellowish spots at the base of the apical setae, the frons is brownish posterolaterally, the mediotergite and anatergite are only brown dorsally, and the epandrium is entirely yellow.

Figures

FIGURES 113 – 119. Allometopon horridum spec. nov., holotype; 113: photo, dorsal; 114: same, lateral; 115: external genitalia, left lateral; 116: same, posterior; 117: inner surface right surstylus; 118: internal genitalia, ventral; 119: same, left lateral.