bit of a grim post this one.
I found some painted lady caterpillars on thistles and noticed that next to one of them, was a large cotton-wool like ball. on closer inspection, I noticed that the “ball” was moving and contained small (about 3-5mm) maggot-like larva. the caterpillar seemed to be alive, but promptly fell off the food plant, leaving the “ball” on the plant.
later when trying to find what it might be, I read that several butterfly larva are parasitised by braconid and chalcid wasps and tabanid flies, but couldn’t find any names species that specifically parasitised the Painted lady.
if anyone knows what species this might be it would great if you got in contact – details on right or leave a comment below. thanks.