Dorsomitus Michel & Tjeder 1992

Dorsomitus Michel & Tjeder † gen. nov.

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Figs 1–3

Dorsomitus Tjeder, 1992: 25 –26, figs 50–51. Nomen nudum.

Type species

Disparomitus neavei Kimmins, 1949, here designated.

Diagnosis

The genus Dorsomitus gen. nov. is well characterized by the combination of the following characters: the markings on the third abdominal sternite in both sexes (Figs 1E, 2F, 3C, F) and the shape of the first abdominal tergite of males being prolonged into a strong, apically forked projection directed backwards with the apex of each prong covered by dense short black hairs directed downwards (Figs 1C–D, 2C–E).

Description

H EAD. Frons with a tuft of white erect setae on each side and a tuft of brownish setae between antennal bases. Antenna straight, shorter than distance between base of the forewing and pterostigma. Third segment of labial palpus without sensory pit.

THORAX. Lateral and ventral surface of thorax covered with long white setae (Figs 1B, 2B). Wings hyaline. Pterostigma short, yellowish to light-brown with four cross-veins heavily bordered with dark brown.

L EGS. Femora covered by long white hairs. Tibiae with dark brown spine-like hairs ventrally, each side with long white hairs and dorsal surface glabrous.

ABDOMEN. First abdominal tergite of males prolonged into a strong, apically forked projection directed backwards with apex of each prong covered by dense short black hairs directed downwards (Figs 1C– D, 2C–E). Sternite 2 with the posterior margin indented in the middle (Figs 1E, 2F, 3C, F). Sternite 3 with its surface slightly wavy transversally, with a shiny black S-shaped area at the antero-lateral angles and two longitudinal black sinuate lines (Figs 1E, 2F, 3C, F), which disappear gradually on the following segments. Male ectoprocts moderately developed laterally and downwards (Fig. 2G). Gonarcus-parameres complex as in Fig 2H–J. Parameres not prolonged downwards by a carina (Fig. 2H, J). Female with head and thorax of same coloration as male (Fig. 3A, D). First abdominal tergite not developed dorsally, divided along the midline into a pair of dorso-lateral plates united by membranous tissue (Fig. 3A–B, D–E). Third abdominal segment shorter than in male (Fig. 3C, F). Coloration of abdomen as in Fig. 3.

Tribal position

It is not possible to assign the genus Dorsomitus gen. nov. to a known tribe with certainty, given the lack of recent taxonomic work. The most closely related tribes seem to be Suhpalacsini and Acmonotini described by van der Weele (1909). However, according to this author, in the former tribe the ectoprocts are small and not expanded (“klappen-förmige Appendices”) and the basal tergite of the abdomen is never developed into a cone-like projection, and in the latter tribe it is the second and not the first abdominal tergite which is dorsally developed. Navás (1919) grouped both tribes in Suhpalacsini to include his new genus Fillus Navás, 1919 from Argentina, considering it closely related to Disparomitus van der Weele, 1909 and Acmonotus MacLachlan, 1873. The genus Fillus is characterized by the first abdominal tergite elongated and folded horizontally on the second and third abdominal segments. The extremity of the protuberance is weakly forked, but is devoid of spines. The genus Dorsomitus gen. nov. could fit Navás’ description, but this clade is probably not monophyletic and further investigation is needed to provide comprehensive phylogenetic relationships between the genera, and to assign Dorsomitus gen. nov. to any existing tribe with certainty.