Mesembrinellidae Shannon, 1926

Whitworth, Terry L. & Yusseff-Vanegas, Sohath, 2019, A revision of the genera and species of the Neotropical family Mesembrinellidae (Diptera: Oestroidea), Zootaxa 4659 (1), pp. 1-146 : 16-18

Family Mesembrinellidae Shannon, 1926

Diagnosis. This is a morphologically diverse family with species ranging from 7 to 17 mm in body length, sharing many characters with Calliphoridae . Thorax usually subshiny, blue, tan or brown, sometimes with pale to tan tomentose stripes. Abdomen often with shiny blue to brown cuticle with pale tomentum. Anterior thoracic spiracle normally ovate, with a broad oval opening above ( Fig. 5); in a few species the anterior spiracle has a long, narrow opening gradually widening above ( Fig. 6). Posterior thoracic spiracle varying in size from small to large, reniform (= kidney-shaped), with an opening midway along upper margin and a fringe of long, ventrally-directed setae ( Fig. 7). Most species have a subscutellum ranging from weakly to moderately or prominently developed, different from the closely related Calliphoridae where the subscutellum is not developed or at most weak. Row of meral setae in shape of an inverted L, with setae ranging from pale and fine to dark and stout ( Fig. 7). Horizontal portion of inverted L usually composed of about 5 or more setae, in some species shorter, composed of only 2–3 setae or, rarely, absent. Wing with bend of vein M evenly curved (usually forming an obtuse angle, Figs 1, 3) in most species, vs. normally angulate (at a right or acute angle) in Calliphoridae ( Fig. 4). Frons width typically much narrower in males than in females, with frons to head ratios often providing valuable species-specific characters. Female frons broader, with width ranges often overlapping between species. Female with cruciate (crossed) setae just anterior to ocellar triangle. Male terminalia: most species with a roughly rectangular or square-shaped epandrium and medium-sized surstylus and cercus, adjacent at base ( Figs 15, 55, 63, 87); in the spicata -group the epandrium is elongate and the surstylus and cercus are tiny ( Figs 27, 29); in the bolivar -group there is a narrow neck between the epandrium and the (swollen) base of the cercus, with surstylus and cercus widely separated in lateral view ( Figs 31, 33); in the anomala -group the epandrium is reduced and the surstylus is enlarged ( Fig. 99). In most species the phallus is slender with epiphallus of various lengths and shapes, from long and slender ( Fig. 105) to short and blunt ( Fig. 165); hypophallic lobes often of unique shape from rounded ( Fig. 106) to oval ( Fig. 111) or rectangular ( Fig. 182); in a few species the phallus is highly modified ( Figs 117–120). In males of most species ST1 is broad, ST2–4 are gradually narrowing (e.g., Fig. 239) and ST5 is usually broad and bilobed, sometimes modified ( Figs 239, 245, 247, 249). Female with ST1–5 oval to nearly square or rectangular ( Figs 411–454). Female postabdomen not telescopic; dorsum of ovipositor with large T6, ranging from a flattened (e.g., Fig. 282) to a regular U or V shape (e.g., Fig. 287), often with distinctive spiracles; T7 smaller and either bilobed ( Fig. 282) or divided ( Fig. 289); T8 much reduced, divided ( Fig. 284) or continuous ( Fig. 303); epiproct and cerci as in Figs 282–325. Venter of ovipositor composed of ST6, ST7, a greatly reduced ST8, and hypoproct ( Fig. 326). Spermathecae (three in number) of three distinctive types: filiform ( Figs 375–396; most species), tuberform ( Figs 370–374; genus Laneella , though significantly shorter in L. fuscosquamata ), or bulbous ( Figs 397, 410; M. flavicrura and Souzalopesiella facialis ).

Status of genera in Mesembrinellidae . Several studies have questioned the validity of most of the genera in the family ( Vargas & Wood 2009; Moll 2014; Marinho et al. 2017). It has even been argued that only the genus Mesembrinella should be retained as valid ( Cerretti et al. 2017). We accept Marinho’s synonymy of Eumesembrinella with Mesembrinella ( Marinho et al. 2017) . Based on our study of specimens of most previously described species and of the fifteen new species described herein, we retain three subfamilies, Laneellinae, Mesembrinellinae and Souzalopesiellinae, and three genera, Laneella , Mesembrinella and Souzalopesiella . We synonymize the genera Albuquerquea , Giovanella , Henriquella , Huascaromusca and Thompsoniella with Mesembrinella , and species of Mesembrinella are classified within six groups: the M. latifrons -group, the M. spicata -group, the M. bolivar -group, the M. aeneiventris -group, the M. bicolor -group, and the M. anomala -group. These groupings help us discuss species in a logical manner, but they are tentative and we are aware that future phylogenetic studies may suggest further changes in the classification. Characters of each species-group are discussed in detail further on.

Remarks. The detailed key below can be used to separate Mesembrinellidae from Neotropical Calliphoridae . The reniform posterior spiracle readily distinguishes mesembrinellids from calliphorids, sarcophagids and tachinids. Other features of sarcophagids are the three conspicuous black stripes on a gray- to gold-pruinose thorax and the checkered abdomen. Sarcophagids typically also have two larger and two smaller notopleural setae on the notopleuron, whereas mesembrinellids have only two stout notopleural setae. Tachinids have a prominently developed subscutellum, rare in mesembrinellids, and normally they have a bare arista (except in Dexiini), which is setose in mesembrinellids. Other similar flies include muscids, which sometimes have a posterior spiracle similar to mesembrinellids but lack meral setae, always present in mesembrinellids.

The keys to genera and species of Mesembrinellidae provided herein were developed following Guimar„es (1977), and are the first comprehensive taxonomic keys for the family Mesembrinellidae published since then.