Diptera.info

Posted by Sundew on 15-07-2010 17:48

Hi,
This Cylindromyia was feeding on Cirsium arvense flowerheads today. I srill have difficulties to distinguish the species, as I do not know which characters are especially important to depict. Is an ID possible?
Many thanks, Sundew

Edited by Sundew on 15-07-2010 17:48

Posted by ChrisR on 15-07-2010 17:55

To my mind it is Cylindromyia auriceps :)

The key basically asks the following questions on the way to auriceps:

1. Does the hind tibia have a postero-ventral bristle? YES (very hard to see usually)

7. Apical scutellars present? YES

9. (lots of really horrible features to see) BUT on females (this has very small pulvilli and small tarsal claws so it is female) auriceps has those small spikes/bristlets on the underside corners of tergite-2 ... you can see them clearly on the last photo.

:)

Cylindromyia spp. are not easy and some are awkward even with specimens but this sequence of photos seems convincing enough to me ... and C.auriceps is the commonest species, in my experience :)

Edited by ChrisR on 15-07-2010 17:57

Posted by Sundew on 15-07-2010 18:02

Wow - great! That's very helpful indeed. At least C. auriceps should now be recognizable to me - if it poses willingly for underside photos :D.

Posted by ChrisR on 15-07-2010 18:05

Assuming that Theo agrees with me - otherwise I'll look very silly :D Cylindromyia really need a lot of photos from every single angle you can manage - even if it looks completely useless. The features we use are scattered all around the body from the head to the tips of the back legs ;)

The key in Tschorsnig & Herting (1993) is very good if you are in the north. Otherwise I have to use Die Fliegen, which is much harder.