Ischiolobos, Londt, 2005

Londt, Jason G. H., 2005, A review of afrotropical Afroholopogon Londt, 1994 with the description of a new genus and new species (Diptera: Asilidae: Stenopogoninae), African Invertebrates 46 (1937), pp. 203-252 : 231-232

Ischiolobos gen. n.

Etymology: Gr. ischion (hip) and lobos (elongated projection). Refers to the elongate process on the anterior face of the metathoracic coxae.

Type species: Heteropogon holcocephaloides Lindner, 1955 by present designation.

Description: Members of this genus are generally similar to species of Afroholopogon and will key to that genus in the most recent generic key (Londt 1999). That key requires updating to include Ontomyia Dikow & Londt, 2000 , and Oligopogon Loew, 1847 after its transfer to the Stenopogoninae by Geller-Grimm & Hradský (2003). The genus therefore combines the following features: (1) The mesonotum is not greatly elevated and humplike (as in Oxynoton Janssens, 1951 ); (2) The postmetacoxal area is membranous (although this feature is shared with most other genera of the subfamily, it is of special importance because the species of Rhabdogaster , characterised by the possession of a sclerotized postmetacoxal bridge, are very similar and frequently confused with species of Afroholopogon and Ischiolobos ); (3) The pulvilli are well developed (thus differentiating these taxa from superficially similar taxa such as Acnephalum Macquart, 1838 , Ammodaimon Londt, 1985 and Sisyrnodytes Loew, 1856 ); (4) The anal lobe of the wing lacks a bordering vein, i.e. the costa terminates at or before the point where the anal vein joins the wing margin; this character is particularly important as it separates these taxa from palaearctic species of Cyrtopogon Loew, 1847 , Heteropogon Loew, 1847 and Holopogon Loew, 1847 as discussed by Londt (1994).

In combination the following features are diagnostic for Ischiolobos : (1) The metacoxae have, on the anterior surface, an elongate, distally rounded peg-like process ( Fig. 5 ). Care needs to be taken when viewing these structures. While they can usually be seen when viewing specimens laterally, these processes may be at least partly hidden by the mesocoxae as they tend to project into the space between the meso- and metacoxae (this is best seen ventrally). Although this character is found in a wide range of other asilids, it appears to be restricted to only a few afrotropical stenopogonine genera. A survey demonstrated their existence in species of only two other genera, Hypenetes Loew, 1858 and Trichoura Londt, 1994 ; (2) Female hypopygium with poorly-developed distal valves ( Figs 63–64 ). In comparison with species of Afroholopogon , the hypopygial valves are small and not markedly distolaterally compressed to form a V-shaped structure (e.g. as seen in A. capensis – Figs 61–62 ); (3) Male genitalia have a suite of characteristics that when found together are diagnostic: (a) The hypopygium is rotated through about 180°. While a number of Afroholopogon species also share this character, many do not; (b) The epandrium projects beyond the levels attained by either the gonocoxites (including gonostyli) or hypandrium and is usually weakly lobed and shaped like an inverted bowl ( niveoscutum , and to a much lesser extent notios , do however have more obviously defined epandrial lobes); (c) The gonocoxite when viewed laterally has a simple appearance in that it is unilobed distally.Again some Afroholopogon species share this character, but many do not; (d) The hypandrium is relatively poorly developed, being wider than long in ventral view and not projecting distally to the level attained by the gonocoxites. The mediodistal tip is pointed in ventral view and, when viewed laterally, it is upturned and lies between the gonocoxites (often hidden from view); (4) Mystax poorly developed below antennal sockets. The mystacal macrosetae are arranged ventrally above the epistomal margin. Much smaller setae are found halfway up the face and those in the upper region of the face, below antennal sockets, are tiny and somewhat adpressed to the facial surface. While some species of Afroholopogon have mystacal setae that are either widely separated in the middle and upper parts of the face or small and weakly developed, most have a relatively well-developed mystax; (5) Mesonotal pruinescence is extensive. Both holcocephaloides and mesotopos possess a completely pruinose mesonotum. While notios has extensive mesonotal pruinescence there are well-defined apruinose spots, niveoscutum is exceptional in having a far more extensively apruinose mesonotum and is therefore comparable to the vast majority of Afroholopogon species ( A. mauros being exceptional in having an almost entirely pruinose mesonotum).

Ischiolobos may be keyed by adapting Londt’s (1999) key as shown below.

13 Mesonotum greatly elevated anterodorsally and hump-like (2 species – Londt 1996)

........................................................................................ Oxynoton Janssens, 1951 – Mesonotum not hump-like, but of more usual form ......................................... 13a 13a Metacoxae with elongate, distally rounded, peg-like process on anterior surface

(4 species – Londt this paper) .................................................. Ischiolobos gen. n. – Metacoxae lacking peg-like process on anterior surface (18 species – Londt this paper) ......................................................................... Afroholopogon Londt, 1994

Figures

Figs 1–6. (1) Diagrammatic representation of how the basal angle of the fourth radial cell (r 4) was measured; (2) Afroholopogon fugax (Loew, 1858), entire male,Akkerendam Nature Reserve;(3) Afroholopogon uranopia sp. n., male head, paratype, Graaff-Reinet; (4) Afroholopogon vumba (Oldroyd, 1974), wing, holotype; (5) Ischiolobos holcocephaloides (Lindner, 1955), left metacoxa, Mkuzi male, showing anterior peg-like process; (6) Ischiolobos mesotopos sp. n., entire male, holotype.

Figs 58–64. Afroholopogon and Ischiolobos species, genitalia:(58–60) A. xeros sp. n., male genitalia, paratype, 52 km W Outjo: (58) lateral, (59) dorsal, (60) ventral; (61, 62) A. capensis (Lindner, 1961), female genitalia, 9 km SW Willowmore: (61) lateral, (62) ventral; (63, 64) I. mesotopos sp. n., female genitalia, paratype, Queen Elizabeth Park: (63) lateral, (64) ventral. Scale lines = 0.5 mm.