Bandella, Bickel, 2002

Bickel, Daniel J., 2002, Bandella, A New Hilarine Fly Genus from Australia (Diptera: Empididae), Records of the Australian Museum 54, pp. 313-324 : 314-317

Genus Bandella n.gen.

Type species. Bandella allynensis n.sp.

Diagnosis. Flies in the tribe Hilarini ; mesonotum glabrous, without pruinosity, but with species diagnostic colour patterns present; mesonotum with ac and dc reduced to setulae, and posterior slope covered with field of scattered setulae; tibia I without distinct anteroapical comb; male basitarsus not swollen; costa circumambient, although reduced in thickness along posterior margin; Sc incomplete; R 4+5 branched, with R 4 diverging at 45° angle and slightly sinuate, and R 5 ending behind wing apex; CuA 2, strongly recurrent; vein CuP present as distinct vein across cell cup; abdomen terga without strong marginal setae; tergum 7 often with U-shaped median excavation; tergum 8 usually with lateral flaplike projections; hypopygium can flex anteriad at rest; male cercus divided into short basal plate and digitiform clasping cercus.

Description. Rather large, body length 7.0–11.5.

Head spheroidal, with convex post-cranium; post-cranium sometimes with distinctive pruinosity, vertex and frons usually shining with little pruinosity; major setae absent; postcranium with scattered pale ventral hairs, postorbitals short; postvertical setae very short, black; ocellar triangle not distinctly raised; ocellar setae reduced to short hairs; frons slightly narrower than ocellar triangle, and with very short hairs along lateral margins; eyes notched laterad of antennae; face as wide as frons and slightly expanded apically, often covered with pruinosity; palp yellow with white setae, curved and slightly clavate; labrum tapering and heavily sclerotised, about one and a half head height in length, and projecting ventrally; labellum separated from and subequal with labrum; antenna ( Fig. 3c) scape about twice as long as pedicel; first flagellomere tapering, longer than scape and pedicel combined, and with short 2–articled apical style.

Thorax. Mesonotum glabrous, without pruinosity, but pleura with pruinosity; mesonotum with species diagnostic colour patterns present, usually similar in both sexes, but sometimes sexually dimorphic; mesonotum with only short setulae and apart from following major setae: 2 posterior notopleural (npl) setae, 1 short postalar (pa) seta, and 1 short posterior intra-alar seta: ac band 3–4 setulae wide, with bare cuticle each side of this band; remainder of mesonotum, including posterior slope covered with field of scattered short setulae; prothoracic collar (pronotum) with some short setae; proepisternum with field of 8–10 pale hairs; scutellum rather weakly developed and with pair of median marginal setae and some adjacent short lateral setae; laterotergite bare; postnotum broad and bulging.

Legs. All tarsi with strong black claws and large yellowish pulvilli; tarsi often curled in repose in dried specimens; FI and TI mostly with short vestiture; TI without distinct anteroapical comb, although some species have irregular setal row of variable length; male It 1 not swollen; TI and each tarsomere It 1–3 with 2–3 pairs of subapical av-pv setae, and It 1–3 with dense ventral vestiture; TII with pair strong av-pv setae; each tarsomere IIt 1–3 with apical setae; IIt 2–5 each slightly flattened with pale ventral pile; FIII weakly expanded in distal third; TIII without strong setae.

Wing ( Fig. 3b); membrane hyaline; costa circumambient, although reduced in thickness along posterior margin; Sc distinctly incomplete; R 1 slightly swollen near join with costa, and brownish stigma present under distal R 1; costa haired, but other veins bare; R 4+5 branched, with R 4 diverging at 45° and slightly sinuate, and R 5 ending behind wing apex; M 1, M 2, and CuA 1 all joining margin; CuA 2, which closes cell cup, strongly recurrent; vein CuP present as almost fully formed vein across cell cup; A 1 present distally only as fold, and arising midway along cell cup; A 2 present as trace; anal angle weak to absent; lower calypter yellowish with yellow setae; halter yellow.

Abdomen. Cuticle glabrous, with little pruinosity; tergum 1 with some pale setae laterally, otherwise abdomen with only short yellowish vestiture, without strong marginal setae; tergum 1 relatively short with membranous median window; abdominal plaques present on terga 2–5; tergum 7 often with U-shaped median excavation; tergum 8 usually with lateral flaplike projections (e.g., 4b,c); hypopygium can flex anteriad at rest; male cercus distinct and divided into sclerotised short basal cercal plate and digitiform clasping cercus; hypandrium keel-like; aedeagus elongate and conforming to curvature of hypandrium, epandrium broad, with distal curved projection; distinct surstylus not evident.

Female oviscapt relatively unmodified, with subequal terga and sterna on segments 9 and 10, and with pair elongate apical cerci ( Fig. 3f).

Etymology. Bandella means “little Banda”, a diminutive derived from Mt Banda Banda, a New South Wales locality where the genus occurs. The gender is feminine.

Remarks

Bandella comprises nine species from mainland Australia and Tasmania . Species occur mostly in wet sclerophyll eucalypt forests and rainforests, and mostly at higher altitudes. Although the genus has an essentially temperate Australian or Bassian distribution of southeastern and southwestern Australia and Tasmania , one species occurs above 1000 m in submontane rainforest in tropical Queensland .

Bandella is best placed in the Hilarini , as discussed in the next section. It is confined to Australia, and is not close to any described genus from temperate Gondwanan regions: New Zealand ( Collin, 1928), Patagonia ( Collin, 1933) and southern Africa ( Smith, 1969). However, based on a shared character, the divided sclerotised male cercus, Bandella possibly has a distant relationship with the endemic Tasmanian genus Cunomyia Bickel.

proboscis of B. albitarsis in New South Wales. Nectar feeding is well known among the Empidinae (e.g., Chvála, 1976). Specimens of B. allynensis have also been taken on sticky traps placed on smooth barked Eucalyptus trunks, which indicates adults occasionally rest on tree trunks.

Mating behaviour is unknown. Males do not have swollen fore basitarsi producing silk for wrapping nuptial gifts characteristic of the complex of genera near Hilara . Of particular interest are the bright silvery pruinose patches present on the head, thorax and legs of both sexes of Bandella albitarsis . These silvery patches may facilitate sexual recognition in flight, especially since incident light would make them appear to “flash” while turning.

Morphological notes and systematic position of Bandella

I presented ( Bickel, 1996) a set of characters useful in separating the two major tribes of the Empidinae , the Empidini and the Hilarini . Since many characters are variable in expression and must be qualified, higher level taxa have to be defined as a mosaic of characters, a “polythetic classification,” no character necessarily being diagnostic for all members (Gauld & Mound, 1982). As so defined, Bandella has the following set of characters that place it in the Hilarini : laterotergite bare; hypandrium forming a curved convex hood over aedeagus; costa circumambient; vein R 1 distinctly swollen before it joins the costa. Bandella does not have the following hilarine characters: tibia I with anteroapical comb of 8–10 short even setae; male cercus small and desclerotised, and fused laterally with the surstylus and epandrium; male basitarsus I enlarged or swollen.

With the large number of undescribed taxa in the Hilarini , both in Australia and throughout the world, it is premature to attempt any phylogenetic analysis of the tribe. However, two important morphological characters should be discussed—vein CuP and the male cercus.

Vein CuP. Bandella is distinctive in having an almost fully formed vein CuP running lengthwise across the centre of cell cup ( Fig. 3b), and not posteriorly close to vein CuA 2 or vestigial as found in some other empidids (e.g., Brachystoma and some Empis , figures in Chvála, 1983). However vein CuP is absent in Hilara , most Empis spp. and the Trichopezinae . By contrast in Bandella , CuP is strongly developed in all species, although it looks almost like a vena spuria, and not carrying haemolymph. Vein CuP is plesiomorphic to the Diptera as a whole and part ground plan for the Diptera wing ( McAlpine, 1981), but its expression is variable in the lower Brachycera. For example, it is variously developed in the Asiloidea, but usually weak and just behind vein CuA 2.

Cercus. Most male Hilarini have a cercus which is rather small, desclerotised, and fused laterally with the surstylus and epandrium (Cumming & Sinclair, unpubl. data). Bandella , by contrast, has an enlarged sclerotised male cercus, which is divided into a distinctive digitiform “clasping cercus” and smaller “cercal plate” (see Fig. 4b).

This cercal form is similar to that of the monotypic Tasmanian genus Cunomyia Bickel (see Sinclair, 1995 and Bickel, 1998 for further discussion), and this shared character indicates a possible close phylogenetic relationship between these two Australian genera.