In July 1998 I found six full grown Red Underwing caterpillars side of Chickenhall Lane in Eastleigh, Hampshire. The larvae were found resting on the bark of tall poplar trees, the caterpillars were excellently camouflaged resting on the tree barks. What amazed me at the time was the fact that the larvae had climbed down such a long way from the top of very mature Poplar trees which had no lower branches of leaves. After feeding in the night they had climbed down to rest during the day where the larvae are safer from predators such as birds. They were all found about 3 to 5 feet from the ground. The larvae were all hiding along a vertical crevice on the tree bark, even a bird such as a treecreeper would find it difficult to spot the larvae.
They are stick like with protruding notches and rough bristles hanging down the side of the larvae, making them masters of camouflage. I remember thinking how very clever this species is. I was pleasantly surprised how large the larvae were and continued to grow from the few I took to hatch out into moths for my photography. The resulting moths which also have excellent camouflage with wings closed resting on a tree, have a wingspan of 80mm. If disturbed in the daytime they open there fore-wings to reveal their red and black-banded under-wings to startle and deter predators, such as birds that might otherwise eat it. I had to photograph the resulting moths in a cage as they are so lively before releasing them in the evening. As well as Poplar the eggs are also laid on the barks of willow trees during August and September then hatching from the eggs in April.