Diamesa Meigen, 1835

Chamutiová, Tímea, Hamerlík, Ladislav & Bitušík, Peter, 2020, Subfossil chironomids (Diptera, Chironomidae) of lakes in the Tatra Mountains an illustrated guide, Zootaxa 4819 (2), pp. 216-264 : 221

Diamesa Meigen ( Figs 9–13 )

Head capsule yellow to dark brown or brown-black with robust occipital margin. Mentum with single or double median tooth (single tooth sometime with small median notch) and 7–11 lateral teeth. Arrangement of mental teeth, however, gives an appearance of 3–6 median teeth. Ventromental plates vestigial to well developed. Mandible with one apical tooth and 4 inner teeth. Premandible apically broad with 5–7 teeth.

Remarks: The most characteristic feature distinguishing subfossil Diamesa from other genera is the relatively large number of uniform mental teeth and remarkably wide occipital margin.

Identification of larval Diamesa to morphotypes/species is very difficult even in recent larvae ( Rossaro & Lencioni 2015). The basic separation of living larvae is based on characters located on the body and follows with those on the head. On the contrary, identification of subfossils is limited to head coloration and few structures, such as mentum and mandible, that are, due to the feeding habit of larvae, often worn.

The following species have been recorded in the Tatra Mts.: Diamesa laticauda Serra-Tosio, 1964 , Diamesa tonsa (Haliday, 1856) , Diamesa vaillanti Serra-Tosio, 1972 , Diamesa steinboecki Goetghebuer, 1933 , D iamesa nowickiana Kownacki et Kownacka, 1975, Diamesa dampfi (Kieffer, 1924) , Diamesa bohemani Goetghebuer, 1932 ( Bitušík 2004; Kownacki 2010, 2011).

Diamesa remains were not abundant, but relatively frequent, found in about one third of the surveyed lakes.

Three morphotypes were distinguished.

Key to morphotypes:

1 Mentum with 5 subequal median teeth; mandible distinctive: first two inner teeth as long or slightly longer than apical tooth.................................................................................. Diamesa bertrami- type

- Mentum with single median tooth; mandible of different shape................................................. 2

2 Mentum with a single notched median tooth wider than first laterals; first inner tooth of mandible is robust, as long or longer than apical tooth;..................................................................... Diamesa Tatra-type A

- Mentum with a single semicircular median tooth subequal to first laterals; first inner mandibular tooth not longer than apical tooth............................................................................... Diamesa Tatra-type B

Figures

FIGURES 9–14. Diamesa bertrami-type: 9—head capsule, A—mandible. Diamesa Tatra-type A: 10—head capsule, A—mandible. Diamesa Tatra-type A: 11—mentum (arrow indicates position of seta submenti). Diamesa Tatra-type B: 12—head capsule (arrows indicate mandible and genal setae). Diamesa Tatra-type B: 13—mentum (arrow indicates position of seta submenti). Pseudodiamesa branickii-type: 14—head capsule (arrow indicates antenna).