Pseudodiamesa Goetghebuer 1939

Pseudodiamesa Goetghebuer (Figs 14–19)

Head capsule yellow to brown with dark brown occipital margin. Mentum with single sharp median tooth and seven pairs of lateral teeth. Median tooth is separated from first laterals by a deep V-shaped notch; second lateral lying dorsal to first lateral seems to be partially hidden behind it. Fifth and seventh lateral teeth shorter than sixth. Ventromental plates joined with median and first lateral teeth extend laterally, so only 2–4 laterals are often visible. Mandible with 4 inner teeth, apical tooth distinctly larger than first inner toot. Premandible with 7–11 teeth.

Remarks: Three subequal teeth on the mentum apex, position of the second lateral tooth, and large ventromental plates are distinctive among the Diamesinae.

Pseudodiamesa remains are usually very abundant in alpine lakes and the intra-genus determination is very important as larvae of species groups differ in their ecological requirements. Since larvae are morphologically similar, reliable diagnostic can be difficult.

Here we follow a combination of morphological differences suggested by Serra-Tosio (1973) and Ilyashuk et al. (2010) and to distinguish two species-groups (P. branickii group and P. nivosa group) that are consistent with morphotypes applied to subfossil material sensu Brooks et al. (2007), i.e. antennal ratio, pecten epipharyngis, labrum, premandible, mandibular seta interna and mentum. Except for mentum, the above mentioned characters are usually missing in subfossils, thus only the morphology of mentum can be used for separating morphotypes.

1 Mental teeth unicolored, black, part of lateral teeth hardly visible in unflatten mentum; labral lamellae absent......................................................................................... Pseudodiamesa branickii - type

- Mentum with a slightly lighter median tooth relative to black lateral teeth, outermost lateral teeth cleraly visible in unflatten mentum; labral lamellae present.................................................... Pseudodiamesa nivosa - type