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Hi,

Does anybody now a simple feature on how to see if a Sargus is a male or a female? The space between the eyes looks always about the same in the specimens that I catch.
Stubbs shows the genitals but I find it hard to link the drawings with these specimens in reality.
(I would like to be 100% sure about some possible S. cuprarius that I caught in the past...)

MVG
NJG
Belgium

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Hi
Within a species, the male frons is narrower than the female. But in some species the male frons can be as broad as the female frons is in other species, so this is not always easy to use! :(
If you look at the tip of the abdomen it is usually possible to see the cerci in the female. These are two-segmented, unlike the male surstyli which are only one-segmented, and more hidden.
Have a look at
http://www.dipter...post_10864
the first picture shows the two segmented cerci clearly (though this is a Chloromyia).
Dissection of the females is not a waste of time, because there are good characters in the genital furca which can be used to separate the species. :)