Gibbasilus alboala, Londt, Jason G. H., 2016

Londt, Jason G. H., 2016, A review of the genus Gibbasilus Londt, 1986 in southern Africa (Diptera, Asilidae), African Invertebrates 57 (1), pp. 67-81 : 69-70

Taxon classification Animalia Diptera Asilidae

Gibbasilus alboala sp. n. Figs 2, 3-6, 20B

Etymology.

L. albus - white, ala - f. wing; refers to the milky white, opaque bases to the wings.

Description.

Based on 2♂ specimens, ♀ unknown.

Head: Black, fine silver pruinose, black, pale yellow and white setose. Antenna: Black, fine silver pruinose, scape and pedicel black setose. Segmental ratios (scape as 1) = 1: 0.6: 1.2: 0.7 (elements of style = 0.1, 0.5, 0.1). Style composed of three elements (small basal segment-like element, long middle rod-like element, terminal seta-like sensory element). Face black, fine dull silver pruinose, profile plane (straight, no gibbosity evident). Mystax long, well-developed, extending from epistomal margin to antennal sockets, macrosetae pale yellow along epistomal margin, otherwise all black. Frons and vertex black, dull silver pruinose, fine, long, black setose. Ocellar tubercle with long, fine, black setae. Occipital region black, silver pruinose, black setose dorsally, pale yellow laterally, fine white setose ventrally. Palpi 2-segmented, segment 1 white setose, 2 black setose. Proboscis shiny black, fine white setose.

Thorax: Dark red-brown to black, fine, dull, silver pruinose, black, pale orange, pale yellow and white setose. Pronotum black, white setose. Mesonotum black, entirely dull silver pruinose. Acrostichals numerous, mane-like, predominantly black except for few white setae anteriorly and a cluster of fine white setae posteriorly. Dorsocentrals well-developed, black, extending both anterior and posterior of transverse suture. Mesonotal macrosetae: Strong, pale orange, 2 npl, 2 spal, 1 pal. Scutellum black, entirely dull silver pruinose; disc fine white setose, 2 long, black apical scutellar macrosetae. Pleura: Dark red-brown to black, entirely dull silver pruinose, pale yellow and white setose. Katatergal setae weak, pale yellowish. Anatergites uniformly dull silver pruinose, asetose. Mediotergite weakly fine white setose medially. Legs: Coxae dark red-brown to black, fine, dull silver pruinose, fine white setose. Trochanters shiny black, apruinose, fine white setose. Femora slightly inflated, dark red-brown to black except for narrow orange distal tip, macrosetae mostly yellowish (except for 3-5 black proximoventral setae on fore femora). Tibiae mostly brown-orange becoming progressively darker distally, macrosetae mostly orange (a few black at distal tip). Tarsi dark red-brown with black and orange macrosetae. Claws dark red-brown to black, pulvilli and empodia well developed, orange. Wings (Fig. 2): Holotype 6.7 × 2.5 mm, paratype 6.1 × 2.2 mm. Veins brown, cells r1 m3 and cua closed and stalked, membrane unstained, entirely transparent except for partly opaque, milky proximal region (including whole of cells bm, cua, and cup and proximal part of br), microtrichia absent. Halter pale yellow to orange.

Abdomen: Entirely dark red-brown to black, extensively dull silver pruinose, except lateral margins of T2 and T3 which are shiny apruinose. Terga fine short white setose, T1-4 with 1-2 laterally situated pale yellow macrosetae (progressively diminishing in size towards terminalia). Sterna fine, longish setose. ♂ genitalia (Figs 3-6): Epandrium about three times longer than deep in lateral view, with widest part proximal to mid-length; moderately broadly rounded distally; lobes gradually diverging distally in dorsal view. Gonocoxite not quite ⅓ as long as epandrium, smoothly rounded distally. Gonostylus elongate, almost half the length of epandrium, of approximately same width for entire length in ventral view, distally with a subtriangular upwardly directed process, best appreciated in lateral view. Hypandrium short, almost three times wider than long in ventral view, distal margin very slightly indented medially. Aedeagus long and thin, slightly dorsoventrally compressed, S-shaped distally, terminating in a 3-pronged tip. Posterior margin of S8 slightly indented medially with a terminal, subrectangular, dorsoventrally compressed process projecting to approximately midlength of hypandrium. ♀ unknown.

Holotype.

SOUTH AFRICA: 1♂ "S Africa: Cape #69 / 1 km W Nieuwoudtville / 31°23'S, 19°06'E 800 m / Date: 4.xi.1991 / Coll: J.G.H. Londt / Caravan Park and area" (NMSA).

Paratype.

1♂ with identical label (NMSA).

Remarks.

This species bears a strong resemblance to condylus sp. n., described below, but is immediately recognised by the milky white bases to the wings. This condition, although unique within Gibbasilus , is encountered in other asilid genera such as Hypenetes Loew, 1858 ( Londt 1985). While it remains possible that the possession of milky wing bases is a variable character I consider alboala and condylus to represent separate taxa until shown otherwise. In the absence of females it is not known if milky wing bases are confined to males.

Distribution (Fig. 20B), phenology (Table 1) and biology.

Known only from the type locality. Collected in November. The general habitat consisted of endemic fynbos plant species and large boulders.