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Hi.

Some of you may have noticed that I have published a paper with the title "Nematode-induced demasculinisation of Dolichopus males (Diptera: Dolichopodidae)" in Zootaxa (1689: 51-62).

The parasite/parasitoid nematodes can have a major effect of the diagnostic characters of the host fly. Many of these 'nematode forms' have in fact been described as new species! Fortunately (for the dolies at least) the nematode is apparently restricted to basic wetlands in the boreomontane zone. It is currently known with certainty only from Scandinavia, but preliminary records have already been made from the central european mountains and from the nearctic.

Although the paper title refers only to Dolichopus, the parasite has a (potentially much) larger host range. I have seen infected Rhaphium and Gymnopternus males and suspect it may not even be Doli-specific.

So, if you work with Diptera brachycera with semiaquatic larvae (or pupae), you may be interested in this paper. If you don't have institutional access to Zootaxa's archive, ask me for a PDF copy.

The photo below shows a typical parasitised male (in this case Dolichopus "cruralis", which is in fact synonymous with Dolichopus lepidus): The coils of a large, cream-coloured nematode can be seen though the tergal membrane. There's a round exit (or entry?) scar visible on the membrane below the hind knee. The male genitalia are unusually small and the rotation+lateroflexion is incomplete. Not all flies are this strongly modified. A large adult Dolichopus (say Dolichopus discifer) with a single parasite can survive with few external signs of attack.