Puss Moth

The caterpillar’s threat display

The puss moth caterpillar is one of the most dramatic-looking larvae in Britain. When young it is dark brown, mimicking bird droppings. As it matures it turns vivid green with a purple-brown saddle on its back. Most remarkably, when threatened, it draws in its head to reveal a fierce, mask-like false face — a ring of pale tissue surrounding dark eye-spots — and raises its red-tipped tails, waving them in the air. Simultaneously it can eject formic acid from a gland near its head. The combination of visual and chemical defences deters most predators.

Cocoon engineering

The puss moth pupa overwinters inside one of the most remarkable cocoons of any British insect. The larva chews bark fibres from its willow or poplar foodplant and mixes them with silk, constructing a grey, bark-textured case that is glued to a branch and almost impossible to distinguish from the surrounding bark. The cocoon is so hard that the emerging moth has to dissolve part of it with a caustic fluid before it can escape.

The adult moth

Adult puss moths are large, furry, and attractively marked — pale grey with dark markings on the forewing and creamy-white hindwings. They are nocturnal and strongly attracted to light. Unlike the larvae, adult moths have vestigial mouthparts and do not feed during their brief adult life. Males emerge a few weeks before females and patrol woodland edges in search of mates.

Willows and poplars

The species is closely tied to willows and poplars for larval feeding. River valleys, fenland edges, and parkland with mature willows and poplars are the best habitats. The larvae are solitary and can sometimes be found by searching willow leaves for the distinctive chewed feeding signs in summer.