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Hi, this was about 3 mms long, on a rock in the mountains, but not far from a lake. Can someone help?

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Sybistroma inornatus Lw. (formerly Hercostomus).

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Sybistroma inornata

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Why isn't it Sybistroma inornatum? Sybistroma is neuter (as in Sybistroma sciophilum (Loew)).

Stephen.

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Stephen, the gender of Sybistroma cannot be neuter, as Meigen (1824) originally included Sybistroma nodicornis in the genus (neuter gender should be nodicorne). Therefore, all -us and -um names must be changed into -a in this ginus.

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Igor, in his revision of the world genera of Dolichopodinae, Brooks (2005, p. 113) transferred the species to Sybistroma and used Sybistroma inornatus.

Stefan

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Thanks Igor and Sefan.

There seems to be plenty of confusion about this! All three genders seem to be in use for different species in the genus; authors who used the neuter probably made the same mistake I did in assuming the etymology had something to do with the Greek stroma (=bed, substrate), but that can't be right, both for the reason Igor gives and because there is no Greek root to account for the 'sybi' bit. Probably Meigen named the genus after a person (or a place) called Sybistrom or something similar, in which case the feminine gender would have been quite natural. I can't see why some authors have chosen a masculine form.

Does Meigen give an etymology?

Stephen.

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Stephen, unfortunately Meigen did not give etymology. And a few species were described originally in this genus with feminine ending (none with masculine one):
Sybistroma americana Schiner, 1868,
Sybistroma setosa Schiner, 1862,
Sybistroma lenkoranica Negrobov, 1979
(http://members.fortunecity.com/grichanov/wScorpiurus.html#Sybistroma)
Henk Meuffels (teacher of Latin) has not found Greek/Latin meenings for this word
(http://members.fortunecity.com/grichanov/aas.htm)