Ischiodon Sack, 1913

Mengual, Ximo, 2018, A new species of Ischiodon Sack (Diptera, Syrphidae) from Madagascar, African Invertebrates 59 (1), pp. 55-73 : 55-56

Genus Ischiodon Sack, 1913

Type-species.

Ischiodon trochanterica Sack, 1913, by monotypy; junior synonym of Scaeva scutellaris Fabricius, 1805.

Differential diagnosis

(adapted from Vockeroth 1969). Small to medium-sized, rather slender species with yellow-margined mesonotum, broad yellow fasciae on abdomen and very large and prominent male genitalia. Face yellow, with or without medial black vitta; eye bare; basoflagellomere large, twice as long as broad, tapering slightly to an acutely rounded apex. Mesonotum shining black with broad, well-defined, pale to bright yellow lateral vitta extending to postalar callus. Scutellum yellow, usually obscurely brownish on disc. Pleuron mostly shining black, except posterior anepisternum yellow on posterior half and katepisternum with a dorsal yellow macula. Dorsal and ventral katepisternal pile patches broadly separated posteriorly. Metasternum bare. Wing with microtrichia greatly reduced, absent from most of basal half and elsewhere very sparse and irregularly scattered. Abdomen elongate, parallel-sided or very narrowly oval, rather flattened, with a strong margin from middle of tergite 2 to the end of tergite 5. Tergite 2 with a pair of separate or narrowly confluent pale maculae; tergites 3 and 4 each with a rather broad, slightly arcuate yellow fascia separated from the base of each tergite. Very often, the black abdominal areas become reddish or yellow towards the abdominal apex, so the pattern is indistinct.

In males of I. aegyptius and I. scutellaris , the ventral surface of the metatrochanter has a slender or moderately stout, cylindrical, apically acute process (calcar) of varying length. In males of I. aegyptius and I. feae , the inner (mesial) claw of the protarsus has a dorsal preapical projection, or flange, which gives the claw a truncated appearance (Fig. 5F).

Etymology.

Ischiodon is derived from the neuter adjective ischion, from the Greek ischion meaning "hip, coxa" ( Brown 1956: 411) and the masculine Greek noun odous (odon), odontos, meaning tooth ( Brown 1956: 807). Thus, Ischiodon refers to the calcar or spur that some species have in the metatrochanter.

Several authors (including the present author) used the species epithet of Ischiodon aegyptium in neuter form. Ischidon must be treated as a masculine gender and all species names must follow this gender except nouns in apposition. Thus, the correct species epithet is Ischiodon aegyptius .