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Hi!
I work on bumble bees, and I find these diptera larvae in the bees' metasomal hemocele (see picture). I guess they are Tachinidae or/and Conopidae, but I need help from you to identify. Unfortunately, bees are usually frozen after sampling, so I can not rear the larvae. I tried, but (following Murphy's law) no one of the bees kept alive were parasitized.

The size do not exceed 5 mm. I also find other larvae, similar in shape, but white, smaller, softer, and with the spiracles connected to bee's tracheal branches by ...funnels?. I found one of each in the same bumblebee, only one time. Commonly seems to be one larve (white or dark) per bumble bee

If somebody can tell me something about their ID, I will be grateful.

Best,

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I haven't seen the pictures yet (try to delete all spaces from the filename), but have you thought about Strepsiptera?

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Now I have seen the photo's, I would vote for Conopidae

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Are there any notable difference between Tachinid and Conopid larvae to be sure? Any key perhaps?

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for family level I use Smith (1989). An introduction to the immature stages of British flies, a must have (and Ferrar 1987 of course) when studying immature diptera.
In Smiths' key Conopidae and Tachinidae are separated as follows (p71):
6. Posterior spiracles each with numerous pore-like openings.....7
- Posterior spiracles each with three slit-like openings.....10
7. Posterior spiracles usually dome-shaped, either with circular wart-like protuberances each bearing several spiracular pores, or with clusters of pores radiating from the ecdysal scar, or with a small stellar process near each spiracular plate, or with a pair of large laterally directed anal vesicles; endoparasites of bees and wasps......Conopidae
- Posterior spiracle otherwise......8
8. Openings of posterior spiracle arranged in three radiating groups; endoparasites of Hemiptera-Heteroptera.....Tachinidae (in part)
- Oestridae/Hypodermatidae (in mammals)

So just on the basis of biology (Conopidae in bees and wasp vs Tachinidae in Hemiptera-Heteroptera), Conopidae seems the most logical. Also Smith (1989) depicted 3 species of Conopidae which, in habitus, looks similar as yours, think anterior part and abruptly smaller posterior part.
I have no knowledge of a larval key for Conopidae. Smith (1989) refers to some papers: Smith (1966) on Thecophora occidens, and Smith & Peterson (1987) provided a key to genera for the eggs and larvae so far described.

Smith, K.G.V. (1966). The larva of Thecophora occidens, with comments upon the biology of Conopidae (Diptera). J. Zool., London 149:263-276
Smith, K.G.V. & B.V. Peterson (1987). Conopidae. In: McAlpine, J.F. et al. Manual of Nearctic Diptera 2. Research Branch Agriculture Canada Monograph no. 28: 749-756.

I think you can download the latter freely from internet, but not sure though.
I hope this will help


edit: I have once downloaded vol 1, 2 and 3 as PDF so if you need it, let me know through PM.

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Many thanks Atylotus! That is exactly what I need. I will also try to post the other pictures soon (white larva connected to bee's tracheal branches).
I`ll send you a PM regarding the pdfs.
Cheers!