Helicosina Kuwahara & Marshall & Yau 2024, gen. n.
Creators: name: Kuwahara, Gregory K.
name: Marshall, Stephen A.
name: Yau, Tiffany
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Sphaeroceridae
Helicosina

description: Genus Helicosina Marshall gen. n.
Type species. Helicosina crena sp. nov. (here designated).
Diagnosis. Helicosina is easily recognized by the combination of a single cruciate pair of interfrontal setae, short face, characteristically curved palpus, heavy pruinosity, strongly flattened notum with two pairs of dorsocentral setae including one small pair on the suture, long mid tibial setae including a midventral in both sexes, a swollen hind femur, and a suite of male abdominal synapomorphies including conspicuously long and narrow surstylus, and a relatively simple S5.
Generic description. Body length: Males 1.5–2.2 mm, females 1.6–2.2 mm. General colour brown to dark brown, legs pale brown to yellow (Figs. 1–2).
Head: Dark brown, ocellar triangle, interfrontal plates, and orbital plates paler; antennae yellow to orange-brown; gena brown to orange-brown. Frontal width 2.2–2.5 × interfrontal height. Interfrontal setae in three pairs, middle pair very large and cruciate; two strong lateroclinate fronto-orbital setae, anterior pair smaller (0.8–0.9 ×) than posterior, and several small fronto-orbital setulae; ocellar setae large and diverging; inner and outer vertical setae very large; inner occipital seta small and fine, outer occipital seta large; postocellar setae minute. Vibrissa large, vibrissal angle relatively long and bare; gena with a slightly thickened, upcurved seta close to lower margin and 5–7 smaller setae along the ventral margin. Lunule broad and flat; face slightly bulging outwards; palpus large, slightly inflated, gently curved with 2–3 ventral setae. Antenna divergent; pedicel subconical with a well-developed preapical seta and 5–6 thickened marginal setae; postpedicel slightly flattened and apicodorsally pointed; arista long-pubescent. Eye with a shallow notch at about level of anterior edge of frons, greatest eye diameter 3.8–4.2 × shortest genal height.
Thorax: Brown; scutum and lower portion of anepisternum dark brown. Notum distinctly flattened. Two pairs of postsutural dorsocentral setae (anterior pair slightly smaller than posterior pair) separated by 4–6 rows of fine acrostichal setulae. Two postpronotal setae, inner seta much smaller and finer; two notopleural setae, anterior notopleural larger than posterior; two stout supra-alar setae; postalar seta large. Katepisternum with a minute anterior seta and a large posterior seta. Scutellum large, broad, flat, semicircular, medial length 0.5–0.6 × its basal width, with four large marginal setae (apical pair 1.6–1.8 × length of basal pair).
Legs: Yellow, femora tan to brown. Fore and hind femora distinctly swollen (more strongly so in males), hind tibia slightly to distinctly swollen and clavate, hind tarsus swollen; apical tarsomere quadrate and slightly flattened, tarsal claws very large and curved. Fore tibia with several slightly enlarged preapical dorsal setae. Dorsal surface of mid tibia with four proximal (three anterodorsal, one posterodorsal) and four distal (two anterodorsal, one dorsal, one posterodorsal) setae; ventral surface of mid tibia with a strong mid ventral seta and a large apicoventral seta in both sexes. Hind tibia with 2–3 erect preapical dorsal setae and a stout apicoventral seta.
Wing (Fig. 3): Slightly infuscate, relatively elongate (length 2.2–2.4 × width). CS2 1.1–1.2 × CS3. Vein R 2+3 sinuate, distal curve much stronger than basal curve; R 4+5 slightly sinuate, meeting costa just before wing tip; costa extending very slightly beyond apex of R 4+5 (1–2 × costal width). M 1 extending beyond dm-m to wing margin as a relatively straight crease; M 4 extending beyond dm-m by 1.2–1.3 × length of dm-m. CuA+CuP long and sinuate as a colourless crease. Alula narrow, subtriangular. Halter knob dark brown, stem yellow to pale brown.
Male abdomen: T2–5 and S2–4 brown to dark brown, broad, slightly desclerotized around margins, uniformly long setose in posterior half. S5 broad, curved, relatively simple, and long setose at least laterally. Synsternite 6+7 well-developed, S6 portion extending dextrally beyond middle of S5. Epandrium relatively large, saddle-shaped, uniformly long-setose; cercus usually fused medially, forming a well-developed subanal plate; subepandrial sclerite thickened medially. Hypandrium well-developed, Y-shaped, anterior apodeme elongate, slightly sinuate, strongly fused to lateral arms, lateral arms fused to anteroventral corners of epandrium. Surstylus large (subequal in length to epandrial height), elongate (height 2.8–3.4 × length) and tapered, largely bare externally with longer setae along inner-anterior edge. Postgonite small, stout. Phallapodeme large, curved. Basiphallus stout, straight to slightly elbowed, sometimes with a posterior patch of dense setulae, usually with a conical epiphallus; distiphallus large and broad, bulbous, largely membranous and supported by several flattened sclerites, laterally and sometimes dorsally setulose or microtomentose.
Female abdomen (Fig. 7): T2–T6 and S2–S6 brown, broad, well sclerotized medially but desclerotized around the margins, uniformly long setose along entire surface. T7 broad, well sclerotized, and uniformly long setose; T8 broad, desclerotized anteromedially and protruding posteromedially (though this may be the epiproct fused to T8) with six long posterior setae. Epiproct absent or fused to posterior margin of T8. Cercus stout, subconical with long dorsal, apical, and apicolateral setae. S7 large (1.5 × length of T7), subquadrate, and relatively densely setose; S8 strongly reduced or absent. Hypoproct broad, U-shaped, densely microtomentose with 8–10 posterior setae. Spermathecae (2+1) stout, bulb spherical/cylindrical with a large and deep apical invagination, stem elongate but thickened below bulb; ducts elongate and membranous.
Etymology. The generic name is a combination of Heliconia (inspired by the discovery that species in this group can sometimes be found in furled Heliconia leaves) and - sina, a frequently used suffix for genera in the Limosininae. The gender is feminine.
Biology. Although we have observed, collected, and photographed some Helicosina adults in furled Heliconia leaves, most of the specimens considered here were taken in Malaise traps, pan traps, or “general collecting”. There are no Helicosina specimens among the tens of thousands of Neotropical sphaerocerids we have collected in traps baited with the “usual” sphaerocerid attractants (dung, carrion), but a few specimens were collected in pan traps set in decomposing vegetative material or “kitchen compost”. It is most likely that Helicosina species develop as microbial grazers in small deposits of decomposing plant material, such as may occur deep in Heliconia furls.
Relationships. Helicosina species have no obvious relationships to other Neotropical Limosininae.Significantly, they lack the asymmetrical anterior epandrial-hypandrial connections that define the largest clade of Neotropical Limosininae (Pterogramma and related genera).
Distribution. Known from Costa Rica, Ecuador, and Panama (Fig. 8).
description: Published as part of Kuwahara, Gregory K., Marshall, Stephen A. & Yau, Tiffany, 2024, Helicosina, a new genus of Neotropical Limosininae (Diptera: Sphaeroceridae), pp. 459-471 in Zootaxa 5523 (4) on pages 460-464, DOI: 10.11646/zootaxa.5523.4.5, http://zenodo.org/record/13949669