Shedding a layer in this heat?

Another hot day with blue skies and despite having taken lots of lovely photos trip to a castle and dynamic earth, it's another bug blip! Sorry, this isn't very clear but watched a sawfly larvae (?) on a grass head doing what appeared to be sit ups! On closer inspection it was shedding, at least I think it was!?

The top photo shows how the skin becomes like cling film as he pulls himself out and the final one shown the cast layer, with head capsule I think.

Maybe a relation...