Thread subject: :: Tachinidae - Gymnosoma ?

Posted by digitalg on 20-08-2006 12:20

Last April or May I was taking some shots and saw thi fly.
I thought "another Ecthophasia" but the fly was pretty so I took the shot anyway.
The other day I was looking over the photographs again and after what I've learned here it does not look like ectophasia anymore!
Those antenna seem longer, the thorax is black with what seems lighter shoulders and the abdomen marks also don't fit those other ectophasia I've seen.

I would go for Gymnosoma, what say you? :)

Thank you

Posted by Zeegers on 20-08-2006 12:29

It is a female, difficult to tell the species, due to the flash on thorax.
Best guess is G. clavatum.

Theo Zeegers

Posted by digitalg on 21-08-2006 16:37

Thank you

I'm going (to try) to abuse :)
I'm a bit confused how females can be told appart from males in tachinidae, I mean, the distance between the eyes doesn't do it the same way as for syrphidae (for instance) and I've seen males bigger and with relatively larger abdomens than females!
Anyone would like to share the knowledge? :)

About the species, what would we be looking for in the thorax?

Posted by Zeegers on 22-08-2006 18:41

Well, there are 2 answers

for Tachinids: look at the abdominal tip. 100 % sure
95 % sure: females have 2 pair of additional bristles on the vertex near the eyes, pointed FORWARD (the proclinate orbitals). Males don't (with 5 % exceptions)

For Gymnosoma:
Males have bicolorous thorax: front golden yellow, back black.
Females have completely black thorax.

Simple comme bonjour (once you know it)


Posted by digitalg on 23-08-2006 14:20

Thanks a lot ...

I'm bookmarking this thread as I'm sure it won't be 'cerebrally' saved for the first time seen :D
I might have some abdominal tips to show here sometime in the future