Mesoconius infestus group, 1922

Marshall, Stephen A., 2019, A revision of the genus Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae), European Journal of Taxonomy 548, pp. 1-126 : 52-53

Mesoconius infestus group

Diagnosis

Members of the Mesoconius infestus group are relatively robust micropezids diagnosed by the combination of a strong katatergal swelling with a nipple-like apex, the absence of outer vertical bristles and the presence of postocellar bristles (missing in two apparently aberrant specimens of one species). The large and strongly twisted anterior part of the hypandrium ( Fig. 25F ) is unique and an extremely distinctive synapomorphy for the group.

Description

HEAD. Two fronto-orbital bristles, lower small, upper large and inserted on epicephalon near level of upper ocelli. Subantennal concavity entirely shiny. Fore tarsus entirely white or yellow, mid femur usually with a single black band; hind femur with one or two black bands (absent in M. fulvus Enderlein, 1922 ); hind tarsomere 1 (or 1 and 2) usually pale.

THORAX. Prosternum microtrichose, but usually without distinct socketed setulae (setulae present in M. triunfo sp. nov.). Scutum densely microtrichose, with rows of small acrostichal and dorsocentral setulae and sometimes with weak patterns of silvery pruinosity; pruinosity usually including a broad presutural dorsocentral vitta, a narrow postsutural dorsocentral vitta and a broad postsutural lateral vitta (absent or indistinct on orange species). Dorsocentral bristle strong, slightly longer than scutellum. Notopleuron with two widely spaced bristles. Scutellum with a pair of long apical bristles (longer than scutellum) and usually with a pair of marginal setulae in addition to a few discal setulae. Vertical row of katepisternal bristles yellow. All coxae with anteroventral golden setae. Wing infuscated, with a discal pale band divided into diffuse spots below R 2+3 and R 4+5; clear spots can be difficult to discern in species with relatively light infuscation.

MALE ABDOMEN. Sternites 5 and 6 reduced, sclerotization of genital pouch thus derived from linear ventral part of S7. Sternite 8 large, usually deflexed and often contrasting with smaller epandrium. Basiphallus very small, frame-like, not extending beyond base of distiphallus. Basal distiphallus broad and short, distally expanding to envelop a phallic bulb characterized by a perforated saddle-like dorsal sclerite and a ventral part from which a long, whip-like distal distiphallus distally integrated with a very broad and characteristically twisted anterior hypandrial margin.

FEMALE ABDOMEN. Spermathecal complex with a relatively short single spermathecal duct and a long, broad, double spermathecal duct either arising independently from a truncate bursa apex or from a short, broad common duct (extension of the bursa apex). Double duct (common duct of paired spermathecae) divided into distinct basal and distal parts that differ in width and texture; stems of paired spermathecae simple or swollen, without convolutions or branches found in M. eques group.

Remarks

This group appears to be monophyletic on the basis of the characteristic male terminalia, especially the unusual twisted hypandrium with the whip-like distal distiphallus normally enveloped by the broad anterior hypandrial margin, the very large S8 and possibly the sclerotized pocket in the right side of male segment 7. Furthermore, species of the M. infestus group sequenced for CO1 ( M. acca sp. nov., M. notacca sp. nov., M. nigricephala sp. nov., M. infestus ) cluster together on a single branch on the maximum likelihood tree ( Fig. 50 ). The M. infestus group includes a few distinctive and easily recognized orange species ( M. nigricephala sp. nov., M. fulvus , M. ujhelyianus Enderlein, 1922 and M. garleppi Enderlein, 1922 ), but other members of the group are dark-bodied and closely resemble M. infestus .

Distribution

As is typical for Mesoconius , species in the M. infestus group generally have restricted high elevation ranges. Most occur in the Andes from Bolivia to Colombia, but one species ( M. triunfo sp. nov.) occurs in southern Mexico, and several species ( M. bicolor Marshall, 2015 , M. hemithorax Frey, 1927 , M. dianthus Marshall, 2015 and M. zadbi Marshall, 2015 ) occur in Central America.

Figures

Fig. 25. Mesoconius infestus Enderlein, 1922 (species complex), internal characters. A. Spermatheca and associated structures, specimen from Bolivia. B–C. Epandrium, hypandrium and associated structures, dorsal and lateral views, specimen from Colombia. D. ♂, apex of abdomen, specimen from Bolivia. E. Epandrium and associated structures, specimen from SierrAzul, Ecuador, DEBU. F. Male terminalia, including S8, specimen from Baeza, Ecuador, DEBU. G. Detail of basal distiphallus and phallic bulb, specimen from Ecuador, DEBU. Abbreviations: bdp = basal distiphallus; c = cercus; ddp = distal distiphallus; e = epandrium; ea = ejaculatory apodeme; ed = ejaculatory duct; hy = hypandrium; p = phallapodeme; pb = phallic bulb; pg = postgonite.

Fig. 50. Maximum likelihood tree from CO1 barcodes. Sequences were aligned using BOLD (amino acid based HMM) and then manually corrected. Maximum likelihood analysis was performed in RAxML (ver. 8.2) using GTR-G with 100 replicates.