Gymnochiromyia tropica, Ebejer, 2023

Ebejer, Martin J., 2023, A first account of Chyromyidae (Diptera: Acalyptratae) from continental Central and South America and some Caribbean Islands, with descriptions of new species, Zootaxa 5319 (3), pp. 301-331 : 306-309

Gymnochiromyia tropica sp. nov.

Figs 4–5

Material: holotype: ♁, VENEZUELA: Cojedes State, Hato Piñero, Llanos plains , 08°56ʹN 68°05ʹW ca. 150m alt. Malaise trap. iii.1991, leg. G.C. McGavin (OUMNH-2005-058), deposited in OUMNH .

Paratypes: 1♁, 5♀♀, same data and depository as holotype .

Diagnosis: A pale yellow species with pale brownish yellow transverse bands on basal abdominal tergites; no presutural dorsocentral setae.

Description

Male.

Head: yellow except for black ringed ocelli; frons relatively narrow, about 1.2 width of eye at vertex and frontal margins converge anteriorly, at level of antennae about 0.7 width that at level of anterior ocellus; gena broad, a little deeper behind, in profile, below middle of eye, about 0.9 height of eye, with several 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 short vibrissal setulae, longest not quite 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 distinct pubescence along anterior margin; 1 st segment of arista yellow, second brown in distal 2/3, 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; about 6 very short and fine white setulae across middle of frons.

Thorax: entirely pale yellow; chaetotaxy: 1 postpronotal, 1 posthumeral, 2 notopleurals, 1 postalar, 0+2 dorsocentrals, acrostichals in 6–8 irregular rows with prescutellars well developed, 1 intrapostalar, 4 scutellars, 1 anepisternal, 1 katepisternal at upper posterior corner with 2 setulae vertically in front.

Wing: veins all pale yellow; distance on costa between R 2+3 and R 4+5 about 0.8 that between R 4+5 and M; distance between cross veins about 1.6 length of posterior cross vein, which is about 0.4 length of apical section of vein Cu. Haltere pale yellow.

Legs: not modified except for slightly thicker femora; 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 relatively few fine pale setulae especially along posterior margins.

Hypopygium ( Figs 4B , 5 ): epandrium distinct; cerci small, pale and densely short setulose posterodorsally; surstylus sinuous at base and curved at apex; hypandrium distinct and broad in lateral view, but parallel sided viewed dorsally; pregonite narrow in profile and bent almost 100 degrees; phallapodeme narrow and elongate; postgonites well-sclerotized and more or less trapezoidal; distiphallus pale, sinuous, tubular, distally poorly sclerotized and apically bifid with membranous epiphallus covering basal part.

Female: as in male, but larger and tending to have setae and setulae more pale brown than yellow; tergites yellow with pale brown transverse bands dorsally; spermathecae dark spherical with translucent, membranous spermathecal ducts.

Body length: male 1.3 mm, female 1.5 mm, Wing length: male 1.2 mm, female 1.6 mm.

Variation: the brown markings on the tergites are absent in some females.

Etymology: the species epithet refers to the tropical origin of this first species of Gymnochiromyia to be found in South America.

Distribution: Venezuela.

Similar species: several Old-World species are entirely pale coloured and have no dorsocentral seta anterior to the scutal suture ( Ebejer 2008, 2010). One, G. pretoriella Ebejer, 2008 has a tubular distiphallus. However, this is much shorter than the same structure in the new species, pigmented, not bifid apically, and smaller relative to the size of its epandrium. The overall appearance and chaetotaxy is otherwise as in G. tropica . Another South African species, G. balteata Ebejer, 2008 also has a tubular distiphallus, which is also short relative to the epandrium, and which has a dark midline mark and is dark along its anterior margin; there are also differences in the other hypopygial structures. G. tropica differs from G. semihirta primarily in the more obvious and more numerous frontal setulae which are proclinate, and in the detail of structures of the male hypopygium.

Notiochyromya Ebejer, 2009

Type species: Notiochyromya tripunctata Ebejer, 2009: 336 , by original designation.

Figures

FIGURE 4. Gymnochiromyia tropica sp. nov., A. holotype, male in alcohol. B. same, abdomen enlarged. C. same, after critical point drying. D. paratype female. E. same, dorsal view.

FIGURE 5. Gymnochiromyia tropica sp. nov., hypopygium of male paratype, lateral view. Abbreviations: as in Fig. 2, psg– postgonite. Scale bar = 0.1mm.