Gymnochiromyia semihirta Ebejer 2023, sp. nov.

Gymnochiromyia semihirta sp. nov.

Figs 1–3

Material: BONAIRE: holotype ♁, Kralendijk, Santa Barbara, 12.192°N, 68.283°W, 21.xi.2022, leg. J. van Blerk, light trap, BON 2022-2023, Museum Leiden (RMNH), critical point dried and card pointed; postabdomen in glycerine on the same pin as the specimen.

Paratype: 1♀, Tera Barra, 1–6.xi.2022, 12.2950°N, 68.3919°W, leg. J.-J. Mekkes & M. Boeken, Malaise trap, 2022-2023.2, Museum Leiden (RMNH), critical point dried and card pointed.

Diagnosis: A pale yellow species with pale brownish yellow transverse bands on abdominal tergites, less distinct in the male; mesofrons entirely devoid of setulae; no presutural dorsocentral setae, a supra-alar seta present; acrostichal setulae in 10 irregular rows; male hypopygium with almost spherical epandrium and relatively large angled surstylus; female abdominal tergite 7 with brown spot dorsally at middle.

Description

Male.

Head: entirely yellow with translucent ocelli; frons, about 1.2 width of eye at vertex and frontal margins almost parallel, converging only slightly anteriorly, at level of antennae about 0.9 width that at level of anterior ocellus; gena broad, a little deeper behind, in profile, below middle of eye, about 0.7 height of eye, with few minute pale yellow setulae; occiput in profile visible behind posterior pole of eye, with short postocular setulae in one irregular row; mouth parts all yellow; 2 very short vibrissal setulae, longest about half as long as anterior fronto-orbital seta; face short, poorly sclerotized and depressed; median carina not developed; antenna yellow, pedicel with distinct seta dorsally; basal flagellomere with fine but barely noticeable pubescence along anterior margin; 1 st segment of arista yellow, second brown in distal 5/6, with fine pubescence; chaetotaxy: 3 strong fronto-orbitals, anterior inclinate, paraverticals short and convergent; 1 inner vertical and 1 outer vertical, both strong; ocellars long, proclinate and diverging; no setulae across middle of frons, but about 6 minute, very pale reclinate setae present in 2 longitudinal rows on each side near eye margin.

Thorax: entirely pale yellow; chaetotaxy: 1 postpronotal, 1 posthumeral, 2 notopleurals, 1 supraalar 1 postalar, 0+2 dorsocentrals—anterior seta about 1/3 length of posterior seta, acrostichals in 10 irregular rows with prescutellars short, 1 short intrapostalar, 4 scutellars, 1 anepisternal with several fine setulae scattered on middle of sclerite, 1 katepisternal at upper posterior corner.

Wing: veins all pale yellow; costal spinose setulae unequal in size and irregularly spaced; distance on costa between R 2+3 and R 4+5 about 0.7 that between R 4+5 and M; distance between cross veins about 1.6 length of posterior cross vein, which is about 0.6 length of apical section of vein Cu. Haltere pale yellow.

Legs: not modified except for slightly thicker femora and tibiae; pale setulae scattered on all pairs of legs, in addition longer setulae present on fore femur ventrally; claws black in apical half and pulvilli normal.

Abdomen: yellow; tergites with pale brown bands and pale brown setulae, longer along posterior margins.

Hypopygium (Fig. 2): epandrium almost globular and covered with numerous fine setulae; cerci pale and short setulose posterodorsally; surstylus long and curved through 90% at middle; hypandrium distinct and, viewed laterally, a little broader at its cranial end; pregonite triangular in profile and fused with caudal end of lateral part of hypandrium; phallapodeme narrow, elongate, ejaculatory apodeme large and sclerotized; heavily sclerotized and large almost circular subepandrial plate lying above cerci; postgonites narrow slightly curved, lying just lateral and a little dorsal to junction of basiphallus and phallapodeme; distiphallus dark brown, bifid to level of basiphallus, sclerotized and deeply pigmented; membranous epiphallus covering basal part, with sclerotization only at apex.

Female: (Fig. 3) as in male, with setae and setulae brown and stronger; tergites yellow with pale brown transverse bands more distinct than in the male; tergite 7 with a dark brown spot dorsally at middle. Spermathecae black and spherical; spermathecal ducts membranous and translucent.

Body length: male 2.1 mm, female 1.4 mm, Wing length: male 1.2 mm, female 1.3 mm.

Variation: unknown.

Etymology: the species epithet refers to the pattern of setulae on the mesofrons, these being placed only on the lateral margins.

Distribution: Bonaire.

Similar species: it is possible that one or more of the three species so far known from the Nearctic Region could be found in the Neotropics. They differ from the new species in that all have setulae on the mesofrons; in addition, G. concolor Malloch, 1914 has 3 dorsocentral setae and a black ocellar triangle; G. flavella (Zetterstedt, 1848) has a presutural dorsocentral seta; and G. nigrimana Malloch, 1914 has 2–3 dorsocentral setae and a black fifth tarsomere of the middle leg. G. semihirta differs from the next species in having a larger, almost spherical epandrium, a larger surstylus and in other details of the hypopygium, particularly the pigmented sclerotized distiphallus. The reclinate frontal setulae next to the eye margin in G. semihirta is a unique feature among all species of the genus.