insect / caterpillar skin ?

insect / caterpillar skin ?

Observation - insect / caterpillar skin ? - UK and Ireland. Description: Buried in garden soil, quite bristly, with small white almost looks like polystyrene balls, but smooth skin inside suggest larva or caterpillar ?

Buried in garden soil, quite bristly, with small white almost looks like polystyrene balls, but smooth skin inside suggest larva or caterpillar ?