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Larva with aphids - Leucopis

Larva with aphids - Leucopis
Montreal, Quebec, Canada
July 30, 2009
This is the same species than this one. I checked many books (Borror, Cranshaw, Wagner (carterpillars), Kaufman/Eaton, etc.) and searched Internet pictures but I have not found any larva with 2 appendages like that. I don't even know if they are antennae or spiracles! Any idea what it it? This larva seems dead but the other one, bright yellow, was amongst aphids (Aphis sambuci), on elder.

Moved from ID Request.

I'm wondering if thats a good idea
Moving an image to a genus we may think it is without being sure might not be a good idea. Perhaps moving it to family or even order level until dipteran expert could confirm would be better.

To address your concern, I have asked Dr. Stephen D. Gaimari to confirm my identification. Yes, it is Leucopis.

Well then ignore my previous statement!
Thanks for addressing the concern of an anal entomologist :)

Its a pupa
Do you still have it? You could collect it and keep it in a container, see what emerges. Then the mystery would be solved once and for all. The two spikes at the bottom of both the pupa and the larva are probably spiracles.

No, I don't have it
I thought it was a syrphid and didn't collect it. But syrphid spiracles are close together, not apart like here.

Oh no I don't think its a syrphid
You're right, syrphid larvae are described as having their posterior spiracles either right next to each other to almost right next to each other. From the other picture of the live larva I was thinking it may be another fly family or the suggestion of some sort of lepidopteran could be correct. This pupa looks more dipteran to me, but I'm not really sure what it is.

I'm wondering if it might be a phorid pupa, but no size indication is given (though compared to the aphids it is about the right size for a phorid). Phorids are so diverse that nothing about them would surprise me anymore.

Ah yes, could be
This larva looks similar to the other picture of the live larva,

Definitely dipteran...
I'm not sure the horns are quite right for a phorid, but I'm not certain that it isn't one either. The only dipteran larva I know of that would be found among aphids, other than a syrphid, is Aphidoletes (Cecidomyiidae). I don't think that's what this is either. I hope somebody knows!

I think I have found what it is.
I first found in the book « Immature Insects, Stehr » an illustration of a fly larva (Leucopis)with 2 long spiracles and then searched and found this web page:

The web site and the book mention that Leucopis larvae prey on aphids.

Thanks everybody for your help.

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