Description of Genus
Megalinga Irwin & Lyneborg
(Diptera: Therevidae: Therevinae)

Megalinga Irwin & Lyneborg (1981: 242) Type species: Megalinga insignata Irwin & Lyneborg (1981a: 244) by original designation.

Derivation of name: megas (Greek) = large; linga (Sanskrit) = penis

Diagnosis: Megalinga Irwin & Lyneborg is associated with the genera Nebritus Coquillett, Arenigena Irwin & Lyneborg, Dialineura Rondani, and Pallicephala Irwin & Lyneborg by possessing fine setae on the posterior surface of the midcoxae and by having the prosternum with fine setae in and around its central depression (except P. quebecensis Webb & Irwin). It is separated from these genera in having a strong black seta present on each of the paired cervical lobes anterior to the prosternum, in having veins R2+3 and R4 with a deep curve before the wing margin, and the male distiphallus being cleft at its apex (see Key to the Nearctic Genera). Because the ground plan for the male terminalia is shared in Megalinga and Arenigena, we tentatively propose a sister-group relationship for these genera.

Medium to large-sized flies. Males more slender and smaller than females.

Description of male and female

Head. Male eyes separated by a distance less than the width of the medial ocellus, facets equal; antenna (Fig. 1), length 0.4-0.5 times head length; scape cylindrical; pedicel ovate; flagellum vase-shaped, tapered apically; style terminal, two-segmented; terminal spine minute; frons in female (Fig. 10) broad, lateral margins convergent dorsally; frontal calli absent; parafacial broad, enlarged ventrally; tentorial pit narrow, deep; maxillary palpus one-segmented (Fig. 2) cylindrical to clavate, apex rounded; setae scattered on female frons; elongate, abundant on gena and maxillary palpus; absent on eyes, parafacial, clypeus, and male frons.

Thorax. Macrosetae: np 2-4, 3, sa 2, pa 1, dc 2, sc 2. Vittae indistinct; prosternal setae elongate; each cervical lobe anterior to prosternum with a strong, black seta; setae abundant on propleuron and scattered over entire anepisternum, absent on remaining pleural sclerites. Wing (Figs. 3, 14; see labelled view of wing) whitish-hyaline with strongly marked pattern of dark brownish patches; veins pale brown; pterostigma brown; setulae absent; length of R4 1.0-1.1 times R5; length of cell r4 1.6-1.9 times width; veins M1, M2, and M3 originate separately from apical margin of discal cell; cell m3 open; discal cell acute basally; cell cup closed with short petiole; m-cu/r-m subequal. Legs. Coxae moderately long; setae elongate, scattered on anterior and posterior surfaces; forecoxa with 2-3 black apical macrosetae and an additional macroseta near base on anterolateral margin. Hindfemur with 5-6 anteroventral macrosetae, some shorter posteroventral setae, often clustered near apex.

Abdomen. Rather narrow, gradually tapering from base to apex; dorsum convex, especially in male; dorsum of male pale, grayish pruinose; dorsum of female yellowish to brownish. Male Terminalia (Figs. 4-9, 15-20). Tergite 8 large, about as wide as epandrium; broadly emarginate posteriorly. Sternite 8 somewhat reduced; posterior margin emarginate. Epandrium shorter medially than wide, posterolateral corners broadly rounded with a broad infolded margin; cercus free, well sclerotized, ending before or slightly beyond hypoproct; hypoproct large, reaching anterior margin of epandrium and attached to anterior margin of dorsal apodeme of aedeagus, entirely membranous. Hypandrium absent. Ventral lobes of gonocoxite very large, attached along midline for some distance and also attached laterally to body of aedeagus; parameral process very long and slender, attached to gonocoxite by a strong medial membrane, but a ventral epandrial sclerite is not evident, thus each gonocoxite is clearly demarcated by a strongly sclerotized and pigmented inner margin; parameral apodeme reduced. Gonostylus elongate with short setae on dorsal and ventral surfaces. Aedeagus attached to parameres and gonocoxites; a long, weak, membranous bridge stretching from distal corners of dorsal apodeme to midsection of paramere and a stronger attachment between ventral lobes of gonocoxites and ventral surface of aedeagus; aedeagus has a very remarkable shape; distiphallus forms a right angle with the heavily sclerotized, rectangular dorsal apodeme and curves downward for about 270 degrees, its apex being cleft; ventral apodeme arises at a right angle from base of distiphallus, extending parallel to dorsal apodeme, but shorter; ejaculatory apodeme about as long as ventral apodeme and very slender.

Female Terminalia (Figs. 11-13, 22-24). Tergite 8 subrectangular, longer than wide, posterior margin broadly concave; setae black, elongate, in broad, dense, medial band and with scattered short, anteriorly directed setae on posterior third of tergite. Tergite 9+10 fused, large with strong acanthophorite setae. Cercus subtriangular, membranous, with numerous, fine, short setae. Sternite 8 large, longer than wide; posterior margin with medial emargination, setae black, elongate, in broad, dense, medial band, with scattered, anteriorly directed setae on posterior third of sternite. Sternite 9 greatly modified, invaginated above sternite 8 to form internal furca which is closed anteriorly; penis guide elongate, tapered posteriorly, attached to base of posterior margin of sternite 8. Sternite 10 membranous; subtriangular; setae short, fine.

Immature Stages. Unknown.

Biology. The two species of Megalinga appear to inhabit different habitats, M. bolbocera inhabits coastal beach hummocks and M. insignata inland dirty washes.

Distribution. Megalinga ranges from El Salvador northward to southern California and southern Arizona. (Map of M. bolbocera; Map of M. insignata)

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Text from Webb & Irwin 1991b