Wildlife Spotting

about 15mm long, found in unimproved grassland, it had crawled to the top of the grass stem for some reason. When found it was a pale-medium tint of green and was almost completely inactive when prodded! Overnight sealed in a plastic container it hadn't moved and had turned this white colour, the first photo is 'enhanced'. I will keep it a while to see what happens. Perhaps shedding skin or pupating? or the victim of an entomopathogic fungus like Beauveria bassiana? 26.10.14 and it still looks like this with it's head poking out of the white body, is it safe to say it is not pupating? UPDATE 28.10.14 i cut it up to try and culture whatever is growing, the caterpillar was hard to cut possibly from dehydration. UPDATE Nov 4th 2014 I placed a small section on some sterilised silkworm pupae and the mycelium has started vigorous growth