I believe this to be a Gypsy Moth caterpillar crawling along under our letterbox. We discovered another exploring our kitchen ceiling on Saturday night and removed it carefully – which is just as well. Its unfriendly appearance (and apparent immunity to predators) is not accidental. When stressed, the fine hairs that cover its back are released and have been known to cause respiratory problems and rashes in people; so no wonder the birds and foxes leave them alone.
It is not small but it is, like the caterpillar in the children’s book, very hungry indeed. This is the impact of a plague of them on the beech hedge out front; which was healthily green until a couple of days ago.
Last night my downstairs neighbour was spraying something on a clutch of them steadily munching their way through the few remaining leaves. They paid no attention and just kept chomping through the leaf, systematically from right to left, leaving nothing but bare brown stalks.
They have now moved all the way down and devastated the hedge in front of the flats either side and are crawling up the outside walls completely impervious to possible predation.