Diptera.info

Posted by Nikita Vikhrev on 07-07-2006 19:18

Moscow region, 06 july, 2-2,5mm
After finishing ID I disovered new Nigel's thread with same fly.
According Tony's explanations:
silvery face
brown dusting restricted to the dorsal surface of tergites
white spots on the wings sometimes almost invisible

Unfortunely I don't know what is"genal bristle".

Posted by Tony Irwin on 07-07-2006 21:40

Hi Nikita
Yes, this is paludum (the upper one is a female, the lower one a male). The genal bristle is located almost directly under the eye. It's the lowest of the series of bristles running down the sides of the face. Your specimens clearly have a weak genal bristle.
Tony

Posted by Nikita Vikhrev on 08-07-2006 13:22

Thank you Tony.
Once again I discovered the main (for me) problem with ID flies on photo. Both images above have been made in same cow's footstep
with 100ml of water. I remembered Ephydridas with darkened wings with white spots. Two my grate astonishment under micriscip I found only 1 out of 4 Ephydridae witu such wings. Another 3 looks with clear wings. Going by key I found that 3 is same as on photo, that wings are dark with white spots, but less visible. Another one is with brown face and good visible genal bristle (thanks once more) pointed foreward and down. I think it is S. stagnalis.
Nikita

Posted by Tony Irwin on 08-07-2006 23:21

In most Ephydridae, the male has a large pre-genital tergite that encloses the hypopygium. Looking at your lower photograph, the joint tergite 1+2 appears just behind the haltere, then tergites 3 and 4, then the large fifth tergite. In the female (top photo) a sixth tergite is visible.
In many species of Scatella there are secondary sexual characters (swollen costa or longer bristles behind the fore-femora), but the sexes in paludum are very similar.
Tony