Allometopon Kertesz, 1906

Owen Lonsdale, 2016, Revision of the genus Allometopon Kertész (Diptera: Clusiidae), Zootaxa 4106 (1), pp. 1-127 : 12-13

Allometopon Kertesz, 1906

Allometopon Kertész, 1906: 321 . Type species, fumipenne Kertész , by monotypy. Melander & Argo 1924: 6; Frey, 1960: 19; McAlpine 1960: 85; Soós 1964: 6, 1984: 11; Sasakawa 1977: 236, 2009: 39; Cogan 1980: 636; Pitkin & Evenhuis 1989: 535; Lonsdale et al. 2010: 256 [phylogeny, key]; Lonsdale et al. 2011 [key].

Diagnosis. Colour often yellow to white with abdominal tergites dark brown; notum with variable brown pattern, but sometimes almost entirely yellow or brown; pleuron sometimes brown in part, at least on anepisternum; wing often partially infuscated. Pedicel with well-developed angulate projection on outer surface and shallower projection on inner surface (similar to Clusiinae and Sobarocephalinae). Usually three pairs of reclinate frontoorbital setae, sometimes two or four. Small interfrontal setae sometimes present, small to minute, near anterior margin of frons. Two dorsocentral setae (sometimes three), usually with anterior dorsocentral half length and closer to posterior dorsocentral than transverse suture. Tibiae with dorsal preapical setae absent. Usually also with first flagellomere ovate, higher than long, arista pubescent to short plumose, and postgena large, triangular.

Description. General. Body relatively small and narrow, with those species with transversely-arranged lateral scutellar setae relatively large and robust; often yellow to white with abdominal tergites dark brown and notum with variable brown pattern, but sometimes almost entirely yellow or brown; pleuron sometimes brown in part, at least on anepisternum; wing often partially infuscated. Scape small; pedicel with well-developed angulate projection on outer surface and shallower projection on inner surface; first flagellomere sometimes small and subcircular, but usually ovate and higher than long, sometimes asymmetrical and more strikingly produced on either dorsal or ventral margin; arista filamentous, pubescent to short plumose with hairs usually sparsely arranged, emerging near midpoint of first flagellomere or slightly above; white basally. Eye often relatively wide and shallow, angled, leaving large triangular postgena. Parafacial, gena and postgena usually silvery tomentose. Face flat, usually weakly sclerotized. Clypeus small and U-shaped, often recessed, usually thicker and enlarged in females. Palpus well-developed, usually slightly flattened.

Chaetotaxy. Frons sometimes with one pair of small interfrontal setae; usually with scattered minute setulae. Usually three fronto-orbital setae, sometimes four or two; all reclinate, usually decreasing in height anteriorly. Ocellar and postvertical setae small, divergent, strong or minute to absent. Vibrissa well-developed, usually one pair, but sometimes two or four; genal setae relatively strong. One postpronotal seta; two notopleural setae; presutural supra-alar seta rarely present ( A. nobile , A. hauseri ); one postsutural supra-alar; one post-alar seta; one intra post-alar seta; prescutellar acrostichal seta sometimes present; one apical scutellar seta; one or two lateral scutellar setae; one proepisternal seta; one anepisternal seta; one katepisternal seta. Dorsocentral setae usually closely spaced near posterior margin of scutum and with anterior dorsocentral usually no more than half length of posterior dorsocentral, sometimes widely spaced with anterior seta up to 3/5–3/4 length of posterior seta; third smaller dorsocentral sometimes present. Tibiae without pronounced dorsoapical setae; mid tibia with large ventroapical seta. Larger specimens with developed setae on posterodorsal surface of fore femur.

Male abdomen. Tergites 1 and 2 fused; tergites 3–6 and sternites 1–5 separate, well-developed with tergite 6 shorter. “Annulus” made up of sternites 6–8, with sternite 8 setose, dorsal, and sternites 6 and 7 ventral and left lateral (respectively) and more weakly sclerotized. Epandrium well-developed, dome-shaped. Cercus small, setose, sometimes partially fused. Surstylus usually well-developed, setose, sometimes enlarged or variably elaborated; inner surface along apical and posterodistal margins usually with small tubercle-like setae. Subepandrial sclerite (sternite 10) V-shaped. Hypandrium with well-developed arm, transverse ventral bridge, and small to welldeveloped ventral lobe bearing setae (sometimes similar to enlarged lobe seen in Sobarocephala ). Phallapodeme usually rod-like with broad ventral shield medially to subapically; ventral shield sometimes much enlarged, forming broad, dome-like structure that may support vestige of apical section of rod. Pregonite usually small, setose, plate-like, sometimes fused to hypandrium. Postgonite usually small, lobate and apically to medially setose, sometimes elongate. Basiphallus small, sometimes very short or elongate, fused to small, projecting epiphallus. Distiphallus usually narrow, flat, sometimes thickened, folded or otherwise elaborated. Paraphallus various, sometimes absent or fused to distiphallus; usually elongate and apically tapered with dorsal surface minutely spinulose past base. Ejaculatory apodeme small, narrow.

Female abdomen. Tergites 1 and 2 fused; tergites 3–8, 10 and sternites 1–8, 10 well-developed, separate, with tergites 7 and 8 and sternites 7 and 8 usually narrow, and tergite and sternite 10 small, lobate; cerci narrow, subcylindrical; long, simple membranous region present between segments 6 and 7 and 7 and 8 (but see description of A. palpale ). Spiracles in membrane below tergites or narrowly incorporated into thinner lateral sclerotized margin. Ventral receptacle sac-like, short, curved apically and with short subapical flagellum (typical of most Clusiodinae ; absent in A. palpale ). Spermathecae (2) not telescoped, sometimes constricted basally, pigmented, usually with basal insertion of duct and sometimes basal spots or papillae; duct narrow, clear, usually at least twice length of spermatheca, tapered at base.

Immature stages. Immature stages are unknown for Allometopon except for eggs (approx. 20) retreived here from the abdomen of a female A. perkinsi (ANIC). Eggs are similar to those of other clusiids, being elongate oval, approximately as long as segment 7, clear and with a small, narrow, raised micropyle. The end with the micropyle is narrower and the egg is widest at about ¾ length. There are about 14 shallow longitudinal ridges that are shallowly scalloped except at the apex and base; the ridges sometimes branch or coalesce, reduced to fewer shallower ridges at each end. The surface is minutely patterned with hexagonal to irregular cells (borders raised) that continue over the ridges.