Cypselosomatidae Hendel, 1931

Lonsdale, Owen, 2020, Family groups of Diopsoidea and Nerioidea (Diptera: Schizophora) - Definition, history and relationships, Zootaxa 4735 (1), pp. 1-177 : 34-36

Cypselosomatidae Hendel, 1931

( Figs 205–232 , 413–414 )

Type genus: Cypselosoma Hendel 1913: 105 , by Hendel (1931: 5). Type species of genus: Cypselosoma gephyrae Hendel, 1913: 105 , by original designation.

Cypselosomatidae inlcudes 13 species of small-bodied flies in three extant genera— Clisa McAlpine (2 species), Cypselosoma (2 species) and Formicosepsis (9 species). Species are known from Australia, Lord Howe Island ( Clisa ), Nepal ( Cypselosoma ) and Southeast Asia ( Cypselosoma , Formicosepsis ) to Taiwan ( Formicosepsis ). The monotypic fossil genus Cypselosomatites Hennig was described for Cypselosomatidae ( Hennig, 1965) , but later moved to Micropezidae by D.K. McAlpine (1998b).

D.K. McAlpine (1966) reviewed and keyed the two cypselosomatid genera known at the time, and later briefly treated the family for description of his new genus Clisa (D.K. McAlpine, 1993) . His 1966 paper also contrasted the Cypselosomatidae to the Neriidae and Micropezidae , compared the species of Cypselosoma , and provided thorough notes on the cave-dwelling Clisa australis (as Cypselsoma australe ). Cypselosomatidae was catalogued in the Oriental and Australian Regions by Steyskal (1977a) and Mathis (1989a), respectively. The two species of of Cypselosoma are differentiated by Shatalkin (2014). Formicosepsis was last revised in Andersson (1976), who divided the six species known at the time into two subgenera ( Formicosepsis Meijere s.s. and Lycosepsis Enderlein ), mostly on the basis of an apical tooth on the scutellum and fore femoral spines in Lycosepsis ; Formicosepsis s.s. was split into two species groups. Papp et al. (2006) described three Thai species for Formicosepsis and Lycosepsis , but did not provide an explanation as to why the two genera were given equal generic standing. Recognition of Lycosepsis is probably unwarranted, at least as a full genus, considering both the small number of described species and the uncertain monophyly of both groups.

Biology. Adults, puparia and larvae of the Australian Clisa australis (McAlpine) were discovered by D.K. McAlpine (1966) in a high-humidity section of a cave hosting a colony of the bat Miniopterus schreibersi (Kuhl) . Larvae were found in dung piles on the cave floor, and dung was recovered from the larval gut; adults were observed on and above the cave floor, with specimens sometimes observed copulating on the dung. Specimens have also been recovered over latrines at the edge of forest reserves (D.K. McAlpine, 1993), providing a similar “enclosed, humid environment”. Clisa disneyi McAlpine was collected on Lord Howe Island in a “stunted, mossy rainforest on the summit of Mount Gower”. Larvae of a Cypselosoma species tentatively identified as C. gephryae , some of which formed puparia, were recorded on rotting banana plants by Curran (1931). Formicosepsis species have been found at elevations above 900m near streams in ravines, sometimes near tea plantations ( Andersson, 1976), on foliage in rainforests (D.K. McAlpine, 1998a) and on a cut banana stem ( Marshall, 2012); specimens have also been cultured on dung (S. Marshall, pers. comm.). Malaise trap samples from Thailand suggest that Formicosepsis can sometimes be locally abundant and collected in pans baited with dung.

Immature stages. Puparia and third instar larvae of the Australian Clisa australis were described by McAlpine (1966).

Adult Diagnosis. Cypselosoma ( Figs 205–210 ) and Clisa relatively compact; Formicosepsis ( Figs 211–215 ) more ant-like, somewhat resembling Strongylophthalmyiidae but with head sleeker and wing narrower; 2.5–5.0mm long. Face membranous, at least ventromedially. Interfrontal present ( Fig. 209 ) (likely homologous with anterior fronto-orbital), sometimes minute to absent; 3 latero- to anteroclinate fronto-orbitals; postocellars divergent, removed from ocellar tubercle; vibrissa present. 4–6 dorsocentrals, with 1–2 smaller setae along dorsocentral line anteriorly; 0–6 acrostichal setae, with at least 1 presutural when present. Pleuron only with proepisternal seta and sometimes one or two very small katepisternals. Katepisternum bulging with dorsal margin sharply angled inwards (white region in Fig. 206 ). Femora usually with distinct ventroapical spines; mid tibia with numerous setae. Vein bm-m absent; ultimate section of M 4 usually absent (short in some Cypselsoma) and posterodistal corner of cell dm rounded (angulate in Cypselsoma, but with apex of M bowed); veins R 4+5 and M 1 converging; costa with sc break; vein sc ending freely in subcostal cell ( Figs 413–414 ).

Adult Definition. Body length 2.5–5.0mm. Colour mostly brown to black, often with yellow and white or brownish patches, mostly on head, legs, anterior surface of thorax and dorsum of katepisternum; halter brown to light brown with apex of knob brownish to white. Body relatively small; compact in Cypselosoma ( Figs 205–210 ) and Clisa ; very slender and ant-like in Formicosepsis ( Figs 211–215 ).

Chaetotaxy: 1 inner vertical; 1 outer vertical; 3 fronto-orbitals (proclinate with posterior seta reclinate); 1 ocellar; 1 postocellar (divergent to subparallel, relatively large); 1 interfrontal (smaller than fronto-orbitals and hair-like to inconspicuous in Formicosepsis , but nearly as large as anterior fronto-orbital in Cypselosoma ( Fig. 209 ); likely homologous with fronto-orbital); vibrissa present; back of head sometimes with additional paravertical seta dorsolaterally ( Fig. 208 ); pedicel with line of marginal setae including one large dorsal; several small weak genals, 1 subgenal (possibly enlarged posterior genal setula); postoculars in single line, sometimes setula-like or only present dorsally ( Cypselosoma ); labium usually with one large basal pair of setae and at least one apical pair. 1 presutural intra-alar; 0–2 postpronotals; 2 notopleurals; 2 posterior supra-alars; 0 posterior intra-alars; 4, 5 ( Formicosepsis , Clisa disneyi ) or 6 dorsocentrals ( Cypselosoma and Clisa australis ), including at least one presutural, and Clisa and Cypselosoma with one or two smaller setae in front of anterior dorsocentral; 6 acrostichal setae in Cypselosoma , 1 or 2 presutural to sutural pairs in Clisa , and 0–6 finer pairs in Formicosepsis ; 1 apical scutellar on small tubercle; lateral scutellar smaller than apical if present, sometimes setula-like, sometimes shifted medially; 1 proepisternal (reduced to absent in Formicosepsis ); 0 anepisternals; 0 katepisternals (if 1 or 2 present, then very small and setulalike); prosternum bare. Fore femur with row of stout anteroventral spines, and with at least 1 long, stout, posteriorly directed seta subapically ( Fig. 207 ); mid and hind femora often with 2–5 spine-like anteromedial and anteroventral setae distally (length variable), often on distinct tubercle ( Formicosepsis with only 0–2 spines); hind femur usually with anteroventral of spines distally with one or two of these enlarged ( Formicosepsis also with row of similar posteroventral spines that are sometimes indistinct to absent, and sometimes lacking anteroventral setae). Fore tibial brush discrete, pale, contrasting surrounding dark setulae ( Fig. 214 ). Mid tibia with medial setae dorsally and posteriorly (sometimes reduced to only 1–3 on one or both sides in Formicosepsis ); ventrally with one to several medial setae; apically with at least one distinct anteroventral seta, but sometimes also with several additional small to moderately sized setae around margin.

Head. Antenna porrect to slightly elbowed; first flagellomere discoid; arista bare, inserted basally to submedially. Frons truncated along anterior margin and slightly projecting, slightly narrowing anteriorly; pilose medially, sometimes excluding part or all of ocellar triangle; notum (except Cypselosoma ) and frontal vitta with fine to coarse microsculpturing; ocellar triangle shining, elongate with margins usually indistinct; ocelli shifted anteriorly, removed from postocellars. Ommatidia slightly larger anteromedially in some Formicosepsis . Face membranous (sometimes only weakly sclerotized), excluding well-sclerotized dorsolateral or lateral regions. Gena usually shining and bulging, more than 1/3 eye height, but reduced to narrow strip in Formicosepsis ; postgena and occiput welldeveloped, sometimes broad. Back of head with semicircular carina that is produced into small dorsomedial lobe in Formicosepsis . Clypeus large, broadly rounded; palpus subcylindrical.

Thorax. Notum entirely microsetulose to glossy, or with fine pruinose pattern (some Formicosepsis ); pleuron smooth, mostly glossy with setulae and pruinosity largely restricted to venter of katepisternum. Greater ampulla present. Coxopleural streak usually weak to absent; posterior margin of anepisternum grooved; katepisternum and meron fused; katepisternum bulging with dorsal 1/3 directed inwards, forming broad “shelf” (note white area in Fig. 206 ) (similar but much shallower shelf seen in some Neriidae ); dorsal katepisternal suture short, ending in broad proepisternum. Formicosepsis with developed pronotal collar, and anterodorsal margin of katepisternum and postpronotum wrapping around scutum; thorax and abdomen, long, slender and exhibiting extensive fusion of sclerites. Precoxal and postmetacoxal bridges absent. Prosternum fused to anteroventral margin of fused katepisterna, with discrete bulge between base of widely separated coxae and anteromedial fossa. Presternum sometimes reduced. Scutellum flat to convex, sometimes relatively short; some Formicosepsis with upturned apical spine.

Wing. ( Figs 413–414 ) Clear to lightly infuscated, or clouded with clear bands. Anal lobe and alula well-developed ( Clisa , Cypselosoma ) or strongly reduced ( Formicosepsis ). Vein R 2+3 closely following costa along length; veins R 4+5 and M 1 converging. Vein bm-m absent. Vein r-m sometimes oblique; sometimes short. Cell cu a short, but sometimes nearly reaching level of subcostal vein apex. Ultimate section of vein M 4 usually absent (short in Cypselsoma) and posterodistal corner of cell dm rounded (angulate in Cypselsoma, but with apex of M 4 bowed). Vein CuA slightly rounded to straight. Costa with sc break (sometimes indistinct); vein sc ending freely in subcostal cell. Calypter hairs short.

Legs. Legs slender; femora slender to relatively stout; hind tibia sometimes slightly compressed laterally. Mid tibia swollen in Cypselosoma .

Abdomen. Spiracles 1–6 in membrane, 7 th spiracle enclosed by sclerite ( Figs 217 , 223, 230 ). Formicosepsis with T3 fused to T1+2. Pregenitalic sternites slightly longer or shorter than wide; S1 particularly short in Clisa and Cypselosoma ; sternites of Formicosepsis considerably narrower with midline bare.

Male genitalia. ( Figs 216–222 ) Terminalia essentially symmetrical. S6 with reduced setation; overlapping and partially articulating with S7. S7 ventral, fused with S8 to form complete ring. S8 large, dome-like, with dorsomedial surface pronounced and posterolateral margins with small emargination; with one pair of large, stout setae. Subepandrial sclerite flat, V-shaped, with apical seta. Epandrium shallow and narrow, usually with one pair of larger posterodorsal setae. Cerci narrow, fused via membrane, distal to margin of epandrium. Surstylus as long as cercus, narrow. Hypandrium, narrow, arms fused. Phallic plate very long, narrow, unbroken. Phallapodeme rod-like, without extensions to hypandrium; base deviated and plate-like. Postgonite narrow, band-like, and meeting each other at or near point of fusion to hypandrium. Postgonite short, band-like, with small setose apical bulb; base textured, meeting apex of postgonite. Epiphallus absent. Distiphallus flat and rod-like, sometimes with membranous apical flagellum. Ejaculatory apodeme stout base grading into short, weakly sclerotized and asymmetrical blade; sperm pump clear.

Female genitalia. ( Figs 223–232 ) T7 and S7 fused into complete oviscape that is widest subbasally and strongly tapered apically; 7 th spiracles ventrolateral. Remaining terminalia very narrow, entirely telescoped within oviscape. T8 and S8 divided longitudinally, roughly textured with tooth-like denticles that are also found along intersegmental membrane to segment 10. T10 with two apical setae; S10 with few apical setae and numerous empty sockets extending along most of length onto short internal process with apical disc. Cerci short, approximate and minutely setose. Genital chamber sometimes with weakly sclerotized transverse folds. Ventral receptacle linear, and narrow to relatively broad. 2 clear or pigmented spermathecae; shape sac- or rod-like, with one sometimes atrophied; duct long and thin, or short, flat and folded.

Figures

FIGURES 205–215. Cypselosoma gephyrae Hendel (Cypselosomatidae), male; 205: dorsal; 206: lateral; 207: ventrolateral; 208: head, posterior; 209: head, dorsal; 210: head, anterior. Figs 211–212: Formicosepsis biseta (Papp) (Cypselosomatidae), male head; 211: dorsal; 212: anterior. Fig. 213: Formicosepsis sp., male and female copulating, Philippines. Figs 214–215: F. biseta, male: 214: dorsal; 215: lateral.

FIGURES 216–222. Clisa australis (McAlpine) (Cypselosomatidae), male terminalia; 216: sternites 6–8, ventral; 217: sternite 6 and segment 7 to cerci, lateral; 218: external genitalia, posterior; 219: same, anterior; 220: ejaculatory apodeme; 221: internal genitalia, ventral; 222: same, left lateral.

FIGURES 223–232. Cypselosoma gephyrae Hendel (Cypselosomatidae), female abdomen; 223: ventral (terminalia retracted); 224: lateral; 225: detail of retracted terminalia; 226: segment 10 and cerci, dorsal; 227: same, lateral; 228: same, ventral; 229: internal genitalia. Figs 230–232: Formicosepsis sp., female abdomen; 230: ventral (terminalia retracted); 231: same, lateral; 232: internal genitalia.

FIGURES 411–422. Wings: 411: Fergusonina sp. (Fergusoninidae); 412: Odontoloxozus longicornis (Coquillett) (Neriidae); 413: Clisa australis (McAlpine) (Cypselosomatidae); 414: Formicosepsis sp. (Cypselosomatidae); 415: Pseudopomyza (Rhinopomyzella) nigrimana Hennig (Pseudopomyzidae); 416: Latheticomyia sp. (Pseudopomyzidae); 417: Nartshukia musiva Shatalkin, holotype (Strongylophthalmyiidae); 418: Strongylophthalmyia angustipennis Melander (Strongylophthalmyiidae); 419: Tanypeza longimana Fallén (Tanypezidae); 420: Neotanypeza marshalli Lonsdale (Tanypezidae); 421: Compsobata mima (Hennig) (Micropezidae); 422: Micropeza sp. (Micropezidae).