Thread subject: Diptera.info :: Scatella

Posted by Nikita Vikhrev on 31-08-2006 19:45
#1

Moscow region, 31 aug, 2,5mm
S. stagnalis?
It sits on leach with some reason or without?

Posted by Tony Irwin on 31-08-2006 20:46
#2

Scatella tenuicosta - very similar to stagnalis, but the most distal spot in the wing is shaped like an hour-glass (or Coca-Cola bottle Grin). In stagnalis this spot is more oval. All Scatella feed on diatoms and desmids, so there's no reason for it to be on a leech - perhaps it's just a good place to view the crowd. (The male is on the leech, the female on the leaf.)

Posted by Nikita Vikhrev on 31-08-2006 20:59
#3

What an easy way to separate two species!
Thank you Tony!

Posted by Tony Irwin on 31-08-2006 21:14
#4

I should point out that not all tenuicosta show the "waisted" spot. Some of them have a less obvious triangular spot, but in all the specimens I've seen, the spot widens anteriorly (towards R4+5). In stagnalis the spot can also be various shapes but never widens anteriorly.
And don't forget there are other species with which they can be confused Sad though these two are the most common and widespread.Smile