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I've already said goodbye to Tachinidae until next spring, but now I'm back with images of freshly-emerged (late autumn?) species.
3 specimens, host: Acronicta sp. (A. psi or A. alni, my records are still not too accurate). Size 9mm.

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A dorsal view.

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And the head.
(My 1000th post, and it's a Tachinidae :) !)

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Somewhat similar to Carcelia sp that I posted a few weeks ago, but with Tachinids lets wait for Chris or Theo.

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Well, it clearly is Carcelia and with such nice pictures we might even get a full ID (Carcelia is difficult genus).
The vertex is very small, the basicosta yellow, tibia 2 yellow with 1 ad, humeri dark, and the thorax slightly reddish in front of scutellum leading to

Carcelia rasa (male)

The host is suprising:
Carcelia rasa prefers Lymantriidae.
However, crossing over to other families as expection in known for many species in Carcelia.
C. rasa has two generations each year, but this record is late even for the autumn generation.


Theo Zeegers

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Thank you so much Theo, even down to a species level ID, I'm really impressed :). Concerning the host, now I have some doubts. I fed only 2 spp. of Lymantriidae, L. monacha (infested by a parasitic wasp, emerged on July 14), and C. pudibunda (collected on Sept. 03 on Salix, no articulate further records, but I can check if its pupa is present, it's rather easy to recognize, and then double-check to maybe exclude Acronicta, I fed many of them and the majority was infested, a common case for solitary caterpillars in autumn).

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I'm impressed too - I am not sure I'd like to split rasa, bombylans and puberula without measuring the frons with with a graticule :D Here it is a very rare species and we have been finding more bombylans than rasa in recent years :)

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Thanks for your remark Chris - and some more on host: I remembered also a Leucoma salicis (collected on August 01, there's a remark 'immediately started preparing to pupate' on it, I should check more of my (loose) notes to find out what its fate actually was).

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I can't stop being amazed by the quality of your photos Black! Could you please reveal exactly what equipment you use and what settings for camera, lens, flash ... perhaps in the macro lens thread, in a new thread or in a PM to me if you don't want it to be public!? I haven't been able to take photos with such good lighting, DOF or overall sharpness. I know that most photos are taken in your kitchen, but nontheless that doesn't make the photos less breathtaking. Thanx in advance from a true fan ;)

If Nikita wants to share his equipment too I woudn't mind. I'm thinking of his nice photos of the small Dolichopodidae etc in the wild.

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I consulted H.-P. Tschorsnig (Stuttgart), he is the real expert in Tachinidae.

The chances of C. rasa being bred from Acronicta are in his opinion very small indeed, because Acronicta has been bred many many times and C. rasa never occurred (C. atricosta did once).

There is a small chance that the species might be Senometopia separata.
On the other hand, given the new info by Black, there is the possibility that a Lymantriid was the host after all !

My personal view is that the second option is the most likely.
if th specimen was collected, and/of if we can get a photo of the middle leg in frontal view or back view, we can get to a really positive ID.
I know, you make such great pictures, and then I start complaining about not being able to see the underside of the middel tibia!

Theo Zeegers

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It's the unwritten rule of diptera identification from photos - "there's always 1 more angle to photograph"! ;)

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Thanks to all for your remarks. 2 crex: will inform soon - no secrets. 2 Theo Zeegers: specimens are collected and still alive, will post mid tibia image(s) soon, and it's really nice to have such a comment from Hans-Peter Tschorsnig.

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Here's some views of the right tibia II of a mounted fly - please let me know if that's enough Theo.

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thanks Black,

The middle picture settles it: there is clearly a ventral bristle, in retrospect we could have seen it all along (I noticed it, however, perspective can be very tricky in pictures so I wanted to be very sure).

Implying: Carcelia, not Senometopia
and therefore:
Carcelia rasa it is.

Any news on the host ?

Theo

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If it is a male then the genitalia are usually quite distinctive - to add weight to the identification :) While it is soft just hook out his 'bits' with a fine pin and let them dry. I have some line drawings here somewhere that I can send to you if you'd like to give it a try :)

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Many thanks Theo and Chris. As regards the host, now I'm sure it was Calliteara pudibunda. I will check if I got any males (two specimens are still alive).

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When you find a male to examine just download the Carcelia article from here http://tachinidae...ifrons.pdf :D It doesn't cover all European species but here we are primarily just trying to back-up the suggestion that it is C.rasa, so if the figures look the same as your specimen then it adds weight to the identification :D

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OK thanks again Chris.

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Today I've got the fourth fly. The smallest of the four is 8mm, and they all are females.

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Ahh, it is normal for all flies to be the same sex if they are from the same host. :( The frons is unusually narrow so with nothing more to work on Theo's C.rasa seems the best bet. :)

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So the case is closed I suppose ;) (it's very unlikely I'll see any Tachinidae until late March :( )

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And, to add to Chris, the reddish spot on thorax before scutellum are a typical 'jizz' for C. rasa.
By the way, the headshot is from a male !
Unless I'm very mistaking.

Theo

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Well Theo I thought I checked them all - maybe my examination wasn't too thorough - will look in the evening - I'm afraid it's too late for any manipulations though.

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Yeah, the frons looks exceptionaly narrow for a female. From the Central European key (again assuming that it really does have a yellow basicosta and 1 anterodorsal on the mid tibia):
bombylans: Frons 0.53 - 0.61x as wide as one eye in males, 0.63 - 0.71x in females
rasa: Frons 0.42 - 0.50x as wide as one eye in males, 0.47 - 0.58x in females
puberula: Frons 0.64 - 0.72x as wide as one eye in males, 0.72 - 0.87x in females

But it is a very tricky measurement to get right first time - I have tried it with several experienced dipterists and it took a few goes to get the technique consistent. You really have to look down on the head perpendicularly from above. Then I usually use my zoom and a graticule to make the frons exacty 1 or 2 marks wide - then compare with the clearest eye - allowing for the drift in focus as you look for the widest point :) Would be very interesting to know if it is really a female and it has measurements less than is normal for C.rasa. :D

Just another thought: they are freshly emerged so it might be worth waiting until they are dead and dry before measuring them. By that time the head may have changed shape a little. That's one important thing to remember - keys are always made from dead material, not from photos of living flies! :D

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Chris,

Could you explain why individuals coming from a single host are always of the same sex?

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No :D But I'd like to know if anyone else knows! Theo?

I am not sure if it always happens either but every time I have seen reared material it has always been the same sex.