Are these Tachinids?

jeremiah · #1 (**permalink**) 25-08-2010, 02:35 PM

Are these Tachinids, please? Seveoaks Nature Reserve 24/08/2010.

1) I saw several of these in different places.

2) I only saw one of these. Much smaller than the yellow one above. Sorry about the fuzzy picture.

Miss Caretaker · #2 (**permalink**) 25-08-2010, 03:13 PM

They look like Tachina fera to my untrained eye which are a Tachinid. I saw lots of these nectaring on an umbellifer yesterday during a rare sunny spell and also noticed a couple that looked identical but were only half the size. You can see the size difference in this picture.

Jo

Matt Smith · #3 (**permalink**) 25-08-2010, 04:28 PM

First two photo are of Tachina fera. The second two are unfortunately too fuzzy to get a proper ID from. The fly in the pics is certainly much smaller then the usual Tachina fera going by the size of the flower it is on. It may be a very small one, or it might be something like an orangy Eriothrix rufomaculata, but I can not say for sure.

Could I have the Tachina fera record details for both postings please.

Thanks

Matt

www.tachinidae.org.uk

Miss Caretaker · #4 (**permalink**) 25-08-2010, 05:43 PM

Hi Matt, I've PM'd you the details. Out of interest, do Tachinids emerge at their final size or can they get larger with age? What would make one smaller than others, would it be a small host when in the larval stage or genetics etc?

jeremiah · #5 (**permalink**) 25-08-2010, 09:30 PM

The grid ref for the Tachina fera is TQ 51835 56872.

The smaller one was definitely different from the Tachina fera, it was smaller, the abdomen was rounder, and it was the orange/red colour that attracted my attention. I've googled images of Eriothrix rufomaculata and the black mark on the abdomen of the one in my fuzzy photo looks exactly the same. (The grid ref for it is TQ 52175 57243.)

Matt Smith · #6 (**permalink**) 26-08-2010, 09:11 AM

Like all insects, when the individual becomes an adult, thats it , they can't get any bigger. The exoskeleton does not "grow", so what you see on the flowers is the final size.

Tachinids (and other parasitic species) can exhibit a wide range of adult size. This is proportional to the larval size, some larvae may have had a "better" host than others for some reason and thus got more "food" while they were developing, hence the size differences.