Mesoconius eques group (Schiner, 1868)

Marshall, Stephen A., 2019, A revision of the genus Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae), European Journal of Taxonomy 548, pp. 1-126 : 12-13

Mesoconius eques group

Diagnosis

The Mesoconius eques group is recognizable by the absence of postocellar and outer vertical bristles (thus with only inner vertical bristles on the upper back of the head) and, with a few exceptions ( M. obtusiconus , M. albiseta sp. nov., M. suzukii sp. nov.), the presence of a greatly enlarged, pointed katatergite.

Description

Upper fronto-orbital bristle usually absent (minute in M. suzukii sp. nov., well developed only in M. obtusiconus ); lower fronto-orbital strong or weak, usually inserted in a patch of microtrichia near lower point of epicephalon. Prosternum usually microtrichose and with at least a few fine setulae anteriorly, bare in M. suzukii sp. nov. Wing usually evenly infuscated but sometimes with clear or dark areas; one species ( M. rufithorax ) has dark wings with clear discal spots similar to those in species of the M. infestus group.

FEMALE ABDOMEN. Stems of paired spermathecae usually characteristically folded with multiple processes (except M. suzukii sp. nov. and M. rufithorax ); paired spermathecal duct divided into basal and distal sections (except M. rufithorax ) and arising from apex of narrowed distal part (common duct) of bursa; in almost all species the single spermathecal duct arises from side of the common duct, widely separated from the paired duct.

MALE ABDOMEN. Tergite and sternite 6 well developed, S6 very large (except in M. suzukii sp. nov.). Anterior hypandrial loop narrow and ribbon-like, in contrast to broad scoop-like anterior hypandrium of other species groups. Distal distiphallus usually very long and slender, much longer than basal distiphallus (shorter in M. suzukii sp. nov.).

Distribution

Other than the Central American species M. tigrinus Marshall, 2015 , members of this species group occur only in Andean South America.

Remarks

Mesoconius suzukii sp. nov. is included in the M. eques group because of its head chaetotaxy, even though it lacks the many other putative synapomorphies found in the remainder of the species group. Sequence data ( Fig. 50 ) suggest that M. suzukii sp. nov. does not belong with the rest of the group. The placement of M. rufithorax also needs re-assessment on the basis of more and better specimens. With the exception of these two problematic species, the M. eques group is strongly supported as monophyletic on the basis of the elaborate spermathecal stems, the large and elongate male S6 and the elongate distal distiphallus.

Figures

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.