Larvae ID please.

[Suzanne B]

I saw this larva on some grass and at first thought there was just one, but on further inspection I can make out 2 heads although on the smaller one you can see that the body is withering away.





Any ideas what they are and what has happened?
Thanks

[paul m]

My first thought is sawfly larvae of which, I gather, there are grass sawflies of the genus Pachynematus, [Hymenoptera, Tenthredinidae] - I know no more, or even whether there are European species (sorry, bit busy at the moment).
What is happening is even more confusing! Could be that one has failed to develope properly when shedding its skin? Or has it got a fungal infection? Sorry, no more ideas .....

[charlieb]

Yeah a sawfly - it looks like its failed to shed it's skin properly.

[Suzanne B]

Thanks Paul and Charlie.
I can honestly say that it never occurred to me that sawfly larva shed their skins. I can't think why I didn't know that....but I didn't.
At least that's something else I've learnt today.
Fascinating stuff.