Diptera.info

Posted by John Webley on 21-08-2006 11:53

I had this noted as a hover fly but looking at my books I have doubts and it looks very similar to the one in Stephen's recent thread.
Can someone help please.
It was taken in May last year in Kent UK.
Thanks, John

Posted by Zeegers on 21-08-2006 13:00

Any indication of size ?
It is either Dufouria (which is not so common),
or a special species of Macquartia.
Tachinidae, in any case

My money is on the first

Theo Zeegers

Posted by John Webley on 21-08-2006 13:48

Sorry to be vague on size but my recollection is that was reasonably large. It is sitting on a bramble leaf which gives some idea.
It would be helpful to know what identifies for sure as Tachinidae.
Thanks,
John

Posted by Zeegers on 21-08-2006 14:43

Dear John,

Well, there is no general rule how to recognize a Tachinid.
So let me give some rules of thumb (to all of which exceptions exist !)

-1) any really spiny fly is a Tachinid
(but the reverse is NOT true)

-2) more general, follow the following program:
* is my fly a calyptrae ? Calyptrae should be large, thorax should have distinct transverse suture. YES ->
* vein M has a distinct bend. (no Muscidae/ Anthomyiidae)
YES ->
* postscutellum strongly swollen (difficult to see)
arista generally bare
eyes never trafficlight-red
abdomen often with strong bristles
species not metallic (with 2 exceptions)
YES ? -> 99 % Tachinidae

Have a look at the gallery, Colyer and Hammond or whatever general textbook on diptera.
It still is difficult. Start and get experience, you will learn

Good luck

Theo Zeegers

Posted by ChrisR on 21-08-2006 15:15

Yeah, if you catch a lot of calyptrate flies and examine them for a subscutellum you gradually get a 'feel' for what makes a tachinid... the big problem is the answer to the question "what makes a rhinophorid?!" ;)

Posted by John Webley on 21-08-2006 16:03

Theo, thanks a lot for your help and additional guidance. Much appreciated.
Not able to fully appreciate the reference to Rhinophorids yet but may get there one day.
John

Posted by Zeegers on 22-08-2006 19:37

The answer to the Rhinophorid question is simple but very unscientific:
there are only a few genera and so you learn the genera, recognize the genera and therefore know they should be Rhinophorids.
But I agree with Chris, Frauenfeldia (Rhinophoridae) could easily pass as Tachinid.

Theo