Allometopon malayensis Sasakawa
Creators: name: Owen Lonsdale
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Clusiidae
Allometopon
Allometopon malayensis

description: Allometopon malayensis Sasakawa
Figs 173–183, 340
Allometopon malayensis Sasakawa 1993: 1.
Description. General: Body length 3.1–3.3mm. Arista short plumose. M1+2 ratio 3.9–4.0. First flagellomere broadly lobate ventrally, dorsum narrower but more produced.
Chaetotaxy: Three fronto-orbital setae with anterior seta slightly shorter. Ocellar seta twice as long as tubercle. Postvertical seta minute, hair-like. Interfrontal seta absent. First flagellomere along margin below level of arista with hairs longer than width of base of arista. Anterior dorsocentral half length of posterior dorsocentral; closely set posteriorly. Acrostichal seta not much longer than surrounding setulae. One lateral scutellar seta.
Colour—male: (Figs 174, 175) Setae yellow, darker on abdomen. Head mostly light yellow (white below antenna); ocellar spot slightly larger than tubercle with margins faded and anterior margin tapering to a faint point; posterolateral corner of frons brown, encompassing bases of vertical setae; lateral margin of parafacial, gena and postgena silvery tomentose; back of head with one pair of brown stripes radiating from foramen; first flagellomere white with brown to light brown stripe on dorsal third that is reduced on inner surface and faded on anterior margin; arista white on basal 1/3–2/3. Scutum yellow in ground colour; anterior margin of scutum brown; ventral half of postpronotum white, dorsum brown anteriorly and light brown posteriorly; notopleuron light brown; lateral margin of scutum narrowly light brown, connected basally to one pair of postsutural intra-alar stripes that recede on outer margin to an apical point. Scutellum yellow with lateral corner brown. Metanotum brown with katatergite, anatergite and mediotergite variably yellow. Pleuron and legs white to yellowish-white. Wing faintly infuscated with base and posterior margin clear. Halter white. Abdomen yellow with broad brown stripe dorsally past tergite 1 that is paler past tergite 5(6?); epandrium brown with distal margin widely yellow; surstylus and cercus white.
Colour—female: (Figs 173, 177, 178) Paler females (Fig. 173) as described for male except as follows: body length 3.8–4.1mm; M1+2 ratio 3.3–3.6; setae slightly brownish; dorsal stripe on first flagellomere darker and more defined; spot surrounding ocellar tubercle extended onto frons as orange to dark brown ill-defined stripe that nearly attains anterior margin; frons with brown posterolateral spot extending along eye margin, sometimes reaching base of posterior fronto-orbital; apical ¼–1/3 of palpus dark brown; clypeus with slight orange tint; inner margin of parafacial and ventral margin of gena with shiny orange line; scutum more extensively brown with most of postsutural region brown excluding medial stripe and small yellow anterolateral notch; medial scutal stripes longer; metanotum mostly brown with yellowish lateromedial spots; most of anepisternum and anepimeron dark brown, sometimes excluding dorsal margin; mid tibia with very faint brownish subbasal ring; abdominal tergites dark brown to tergite 5, 6 or 7, with tergites past this narrowly to broadly yellow laterally (more so posteriorly), and tergite 10 and cercus yellow.
Some darker females (Figs 177, 178) further differ as follows: posterolateral corner of frons with brown spot reaching base of posterior fronto-orbital; scutum with medial yellow stripe much narrowed or obliterated posteriorly, and sometimes scutum entirely brown excluding basally narrowed yellow medial stripe; scutellum also with medial yellow stripe much narrowed to absent; metanotum entirely dark brown; medial to subbasal region of tibiae sometimes faintly brownish.
Variation—female holotype: (Fig. 176) While not examined, the female holotype differs from the above description as follows, based on Sasakawa (1993): body length 3.4mm; M1+2 ratio 3.0; ocellar seta approximately 1/ 8 length of posterior fronto-orbital; base colour of antenna orangish; arista only white at base; ocellar spot not larger than tubercle; parafacial and postgena not noted as being tomentose; similar to some darker females described above as follows: frons with brown spot at base of verticals reaching base of posterior fronto-orbital, scutellum and metanotum dark brown, medial yellow scutal stripe tapering to a point anterior to posterior margin, lateral area of scutum dark brown, being brownish on notopleuron and only narrowly yellow lateral to postpronotum, fore and mid tibiae with medial 1/3 infuscated, and hind tibia with medial half infuscated; abdomen dark with tergite 1, posterior margin of tergite 7 and cercus yellow.
Male terminalia: (Figs 179–181) Annulus well-developed. Epandrium wider than long, with broad perianal region. Cerci narrow, nearly united apically. Surstylus narrow and slightly incurved with apex rounded and subtriangular; base broadly rounded, curved inwards; outer surface bare on anterior half, inner distal margin with several minute tubercle-like setae. Hypandrium with small, but pronounced ventral lobe with three small apical setae. Phallapodeme well-developed, rod-like, with ventral shield free and ventrally angled distally. Pregonite broad, membranous, ill-defined and with several medial setae. Postgonite small, narrow, with one medial and one lateral seta. Basiphallus short, stout, fused to moderately developed and produced epiphallus. Distiphallus dark, stout, clavate, with anterodorsal folds and ventrolateral carinae. Paraphallus fused to base of distiphallus, narrow, pointed, with minute dorsal spinules subapically.
Variation: (Figs 182, 183) Male from Kayan-Mentarang Nat. Reserve with slightly shorter scutal stripes and slightly different genitalia: surstylus slightly higher with apex narrower; pregonite with setae scattered and more numerous; ventral lobe of hypandrium more broadly rounded. Malaysian non-type male (poor condition, antenna, mid and hind legs, most setae missing) with scutellum and postsutural scutum brown and dorsocentral stripes complete; terminalia (not dissected) similar to those of typical males, including extruded distiphallus.
Female terminalia: (Fig. 340) Spermatheca approximately 3 times longer than wide, with minute transverse wrinkles that are denser on distal section; distal 2/3 pigmented and basal 1/3 clear and abruptly narrower. Ventral receptacle well-developed with short flagellum.
Distribution: Indonesia (E Kalimantan, Sumatra), Malaysia (Pahang).
Holotype: MALAYSIA. Malaya: Berinchang, Cameron Highlands, 28.viii.1986, M. Sasakawa (1♀, FRIM). [Not examined—possibly lost]
Additional material examined: INDONESIA. Sumatra: E. Kalimantan Kac. Pujungan, Kayan-Mentarang Nat. Reserve, D.C. Darling, lowland diptero. forest WWF station, Lalut Biral vicinity of base camp, log emergence traps, 2°52′N, 115°49′E, vi–viii.1993 (1♂ 4♀, ROME), Sumatra, Aceh Gunung Leuser Nat. Pk., Ketambe Res. Sta., 3°41′N, 97°39′E, 7.ix.1989, D.C. Darling, 1° rainforest, 350m, screen sweep (1♂, CNC; 1♀ ROME), Sumatra, Aceh Gunung Leuser Nat. Pk., Ketambe Res. Sta., 3°41′N, 97°39′E, 9–21.ix.1989, D.C. Darling, 1° rainforest, young forest, Terrace 4, light gap, 350m, Malaise trap head (2♀, ROME; 1♀, CNC), Sumatra, Aceh Prov., Mt. Leuser Natl. Pk., Ketambe Res. Stat., 350m, screen sweep along Alas R., 4.ix.1989, B. Hubley (1♂, ROME). MALAYSIA. Malaya, Pahang, 12 mi E Kuala Kubu: Baharu, 11–12.x.1961, L.W. Quate (1♂, BPBM).
Comments: Allometopon malayensis is best diagnosed by an unusually large, dark, folded distiphallus and a narrow surstylus with a broadly rounded, incurved posterobasal lobe, as well as a number of other minor features such as fusion of the paraphallus to the distiphallus, a broad, membranous pregonite, and a small, stout ventral lobe of the hypandrium.
Despite the heavy reliance on male genitalic features for confident diagnosis of this species, the females treated here as Allometopon malayensis can be assigned with minor doubt on the basis of the elongate ocellar spot that fades and tapers anteriorly (smaller in males), the characteristic thoracic pattern and the small ocellar seta. While the medial stripe on the frons is not mentioned in the original species description, the remaining description, especially the notal pattern, is highly similar to the darker females examined and allows for species placement.
description: Published as part of Owen Lonsdale, 2016, Revision of the genus Allometopon Kertész (Diptera: Clusiidae), pp. 1-127 in Zootaxa 4106 (1) on pages 43-45, DOI: 10.11646/zootaxa.4106.1.1, http://zenodo.org/record/258766