Strange Caterpillar

Strange Caterpillar

Observation - Strange Caterpillar - UK and Ireland. Description: Under an Alder leaf. At first I thought it was a bit of fluff on the leaf but then it started moving. I wondered whether it had some sort of fungus growing on it but it was completely covered!

Under an Alder leaf. At first I thought it was a bit of fluff on the leaf but then it started moving. I wondered whether it had some sort of fungus growing on it but it was completely covered!