Opomydas Curran

J. Wilcox & N. Papavero, 1971, The American Genera of Mydidae (Diptera), with the Description of three new Genera and two new Species, Arquivos de Zoologia 21 (2), pp. 41-119 : 100-102

Genus Opomydas Curran

Opomydas Curran, 1934: 165 (in key), figs. 4, 12 (p. 164). Type-spe­ cies, Ectyph~lS limbatus Williston (orig. des.).

Head in anterior view nearly two times as wide as high; face at antennae about one-half width of head; oral margin at about one-sixth distance from lower eye margin to antennae; gibbosity largely pollinose in males, bare in females, a suggestion of a central vertical groove in some specimens. Stem of proboscis subequal to length of oral cavity, labella attached at apex and extending down on anterior side for about one-third length of stem; palpi slender, about one-half length of oral cavity. Antennal segment 1 cylindrical and about one and one-third times as long as broad; 2 about one-fourth length of 1 and about two times as broad as long; 3 slender and about three times as long as 1-2; club variable, in some males parallel-sided and as long or longer than 3, in others fusiform and shorter than 3, which is also the usual form for the female club (Figs. 29-31).

Mesonotum pollinose, usually denser on lateral margins and dorsocentral stripes; hairs short recumbent to quite long and erect in some males. Scutellum with short discal and marginal hairs. Post-scutellum rugose, entirely or partly pollinose, lateral slopes pilose. Pleura with hairs on episternum-1, dorsal posterior margin of mesopleura, pteropleura, and metasternum. Pollen usually dense above on sternopleura and mesopleura and on metapleura and metasternum.

Abdominal tergite-1a slightly rounded, bare, and occasionally densely pollinose; 1p with short and quite dense erect hairs; remaining tergites with numerous short and recumbent hairs in 0; bullae (Fig. 50) slender and about four times as long as wide. Sternites with very sparse and short hairs except on 7-8, a 8 as long or longer than 7. Female tergites and sternites 2-7 with very short sparse, recumbent hairs, hairs long, numerous and erect on 8, apex with circlet of strong spines. Male genitalia (Figs. 116-118) very peculiarly and characteristically built, and presenting many primitive characters. Hypandrium distinct, only fused to the basistyli by a membrane, otherwise free; trapezoidal in ventral view and bowl-shaped in lateral view. Gonopods very primitively built, as they still possess a dististylus, which is laterally placed, very slender and elongate; basistyli short and thick, beaked apical processes bent inwards. Aedeagus a very long conical tube (almost twice as long as the genitalia), dorsally bent; its basal portion is thicker and has many ridges; dorsal portion of the gonopods united by a bridge behind (dorsad of) basal portion of aedeagus, this bridge also coalesced with basal portion of aedeagus: cerci long and slender, united at base; epandrial halves triangular, apex oblongate, both halves united at base.

Fore and middle legs short and slender. Hind femora quite slender, about seven times as long as wide; hairs usually short and recumbent, but may be long and erect; venter with about 16 slightly tuberculate spines. Hind tibiae with slight ventral keel; apex with slender spur plus one or more apical bristles, in some females spur absent or reduced in size but apical bristles present. Hind metatarsus slender, about six times as long as wide, as long or longer than segments 2-4.

Alulae with dense fringe of squamose hairs. Wings about three times as long as broad; second submarginal cell usually closed, at times narrowly open; posterior crossvein present; ambient vein complete; axillary lobe about as broad as long.

Length: 18-25 mm.

Geographic range: u. S.A. (California to Texas), Mexico (Baja California to Chihuahua).