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I recently collected some large Arctia caja larvae to rear through in an attempt to breed out some tachinids. My first larva pupated on the 5th and yesterday the cocoon started to fill up with dipteran larvae (10 up to this morning).

My question is, is it ok to remove the puparia from the cocoon and rear them indiviudally? I would obviously like to associate individual puparia with their flies if possible.

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I think that is generally Mark Shaw's recommended procedure - put 1 puparium in each tube (bunged with a porous substance like cork and with some tissue paper) ... keep them in a cool, dark, airy shed-type place and see what happens

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Thanks Chris. Any pointers on how long emergence may take? I was going to leave them a couple of days to see if any more appeared and to give them all a chance to pupate properly.

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Not really but, as it is early summer, I'd hope you would see some flies in 1 month? Matt might be better on this as he's read-up a bit more on rearing tachs like Sturmia

The problems usually happen with species that over-winter as pupae.

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The key thing with all puparia is not to let them dry out. I would suspect the puparia you have would emerge this summer, which could mean in a week or two, but that depends on the species..

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Thanks for the advice. I have an outside shed which I can use. Any pointers to stop them drying out? Would I need to, for instance, give them a spray with water or provide an open water container to maintain humidity?

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I certainly wouldn't spray them (in containers they wouldn't dry as fast as they would in the wild and so they'd rot quickly). Usually just storing them in a cool, airy place with 'natural' temperate humidity and temperatures should be enough. You're just trying to mimic the outside world but bearing in mind that a pupa is usually located at ground level mixed in with the leaf-litter where it stays in quite stable conditions - no wide, sudden fluctuations in temperature.

Mark Shaw's rearing shed is constantly shaded by tall trees and bushes ... it has a chicken-wire door and hinged side windows (also lined with chicken wire) that can be opened all summer to let air movement through, but which also keep the rain off. The roof is painted white too - everything designed to maintain stability.

Pupae are placed in glass tubes with cork bungs and laid flat, with the collecting data in the tube so that it doesn't get lost

The whole process is described and illustrated in the AES publication "Rearing Parasitic Hymenoptera" by Mark Shaw (The Amateur Entomologist volume 25).

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Thanks Chris, I will have to invest in that. One last question - presumably I don't just leave the puparium rattling around in the tube, so have you any advice for a substrate or base to lay it on?

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I am pretty sure that Mark does leave them without substrate (less chance of introducing fungus) but I think I would put in a short strip of dry kitchen/toilet tissue, perhaps held in place by the bung and protruding from it a bit - just another way for air to get in and out

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Thanks Chris. I will let you know what happens.

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The flies from the puparia have started to emerge over the last two days. I had 22 in the end, with 11 emerging so far, eight between 5.30 and 7.00 this morning. My question is, how long do I need to leave them to harden up before I can dispatch them? Mark Shaw's book (I bought it!) suggests leaving them to starve, but my wife is following the process and I don't thnk I can get away with that without serious grief!

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Well, I have read that the problem with flies is that sometimes they can take up to 2 days to inflate their wings properly. Mark's technique is probably the best but if the wings are inflated correctly and it looks like a normal tachinid then it should be fine.

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I dispatched one after two days and it still hadn't quite hardened up (or at least the ptilinal suture hadn't closed up properly). Shall try leaving the rest for a few days longer. Got this one under the microscope and it appears to be Huebneria affinis again.

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Out of interest, how many fairly decent specimens of Huebneria do you think you have there? I only ask because the BMNH don't have any collected in the UK and they would be happy for a donation or two for their UK collection

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Around 12 or 13 out of the 22. The reminder have shriveled abdomens and wings and don't look like getting any further (the others seemed fully expanded within an hour or so). I have asked Erica at the BHM if she wants a Huebneria specimen and have filled in the change of ownership form, but intended to drop it off when I go up (which obviously hasn't happened yet!). I will include a couple of this current batch as well.

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Blimey ... you have more British Huebneria in that batch than have ever been caught before OUM have the first British specimen ... you gave me one ... Steve Falk had one just down the coast ... and you have the rest ... well done!! BMNH in Dinton could do with a pair if you can spare them too

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Hold the front page! The second specimen I have looked at appears to be a Carcelia, so it looks as though there may be a mixture of species. Will keep you informed.

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(biting nails)

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All of the other emergees were Carcelia lucorum. Bummer.