Acantothereva Séguy, 1935

Holston, Kevin C., 2009, A new species of Acantothereva Séguy, 1935, from Tunisia (Diptera: Therevidae: Therevinae): taxonomic consequences and phylogenetic implications, Zootaxa 2155, pp. 28-36 : 31-32

Acantothereva Séguy, 1935

Acantothereva Séguy, 1935: 153 . Type species: Acantothereva rungsi Séguy, 1935: 153 , by original designation.

Acanthothereva Lyneborg, 1968: 298. Unjustified emendation. Noted as a “lapsus calami” by Lyneborg (1968: 298).

Diagnosis. Male eyes separated by more than 5X width of anterior ocellus, upper and lower ommatidia of equal size. Posterior margin of head in dorsal view strongly convex; ocellar tubercle slightly raised (the condition observed in most therevine genera) to dilated with ocelli widely separated with posterior ocelli directed posteriorly, upper frons and vertex sunken to distended with respect to eye margin. Antennal insertion low; parafacial setae present; female frons with uniform tomentum. Wing membrane opaque white with dark maculation extensive without forming bands or large contiguous dark regions. Femoral cuticle varying from yellow or yellowish brown to black; tibial apices slightly dilated; subapical macrosetae of tibiae long: protarsus and pulvilli small. Distiphallus hook-like (extending dorsad from base and decurved to apex), laterally compressed with apex broadly rounded to truncate in lateral view. Small species: 6–7 mm.

Comments: Extending on the original description of Acantothereva as a monotypic genus by Séguy (1935), Lyneborg (1968) listed nine “apomorphies” [=synapomorphies], noting that several of these characters are less pronounced in A. punctipennis than A. rungsi . These characters were 1) the broad separation of the male compound eyes, 2) the “elevated” upper frons and vertex with a poorly defined ocellar tubercle, 3) widely separated ocelli with the two posterior ocelli directed posteriorly, 4) a low antennal insertion, 5) maculated wings, 6) the “gradually” dilated tibial apex, 5) tibiae with long subapical macrosetae, 7) small protarsus and pulvilli, 8) a “stout phallus, 9) and the comparatively short dorsal, ventral and ejaculatory apodemes.”

These external characters are useful for distinguishing Acantothereva within the context of the western Palaearctic stiletto fly fauna, but only the morphology of the distiphallus provides an unambiguous diagnostic feature. Broad separation of the male compound eyes is unusual in Therevidae but has been noted for therevine genera readily distinguished from Acantothereva (e.g., Chrysanthemyia ) as well as Neotherevella , which is similar in external morphology to Acantothereva ( Lyneborg 1978, 1983a). An elevated frons and expanded ocellar tubercle is characteristic of the type species, A. rungsi , and less pronounced in A. punctipennis ; the ocellar tubercle of the Tunisian species is unmodified and situated below the dorsal eye margin; and the ocelli are directed posteriorly only in A. rungsi . A low antennal insertion, maculated wings, and dilated tibia apex are present in the Tunisian species, but these characters have been observed across a broad sample of therevine genera ( Lyneborg 1976, 1983b, Gaimari & Irwin 2000, Hauser & Irwin 2004). Although the dorsal, ventral and ejaculatory apodemes in Neotherevella are similar to those in Acantothereva (c.f., Lyneborg 1968: Figs 11–12; Lyneborg 1976: Figs 236, 327), the laterally compressed distiphallus with a broadly rounded to truncate apex is unique to Acantothereva .