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Yerterday, I observed small, probably flightless hironomid males that swarmed, gliding on the water surface of a small lake in Mazury Poland. Manner of gliding still obscure, since I did not notice any wing vibrations. Any suggestion to the species and to the behavior ?

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This must be Thienemanniola ploenensis, a Chironominae with slightly reduced wings "confined to shallow, still waters" of the western Palaearctic. (Cranston et al. 1989)

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Thank you John, in the paper of Gilka and Dominiak (2007) from Fragmenta Faunistica, stays that this sp. is known only from the few European sites so I give coordinates of the place from goole maps: 53.670477,21.212282

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I did not know about the similiar species Corynocera oliveri when I made my ID. Species of Corynocera also swarm on fresh water bodies. This is not C. ambigua, a holarctic species (group) which has a more strongly modified wing.

Thienemanniola lacks hairs on the thorax and has a more slender gonostylus. Corynocera has may have some dorsocentrals and scutellars and has a short, broad gonostylus.

C. oliveri may be a more northern species.

Both genera are in tribe Tanytarsini.