There are about 1500 species found worldwide except in New Zealand, and 12 in Britain. The adults are mainly nocturnal, medium to large sized, brown or brown and yellow, and fat. The adult males have feathery antennae which can detect the scent of a female 100s of metres away. All the larvae are hairy, and these hairs protect them from being eaten by most birds, and can cause irritation in humans. The caterpillar hairs are usually incorporated into the cocoon.
Above is Gastropacha quercifolia, the Lappet moth. It is usually found in scrub, hedgerows, open woodland and sometimes in gardens. It is common in southern England and can be found as far north as Yorkshire.
The eggs are white with grey spots and laid in bands, pairs or small batches on twigs or leaves of the foodplant in July or August and hatch in about 2 weeks.
The caterpillar feeds at night on whitethorn, blackthorn, hawthorn, sallow, apples and other fruit trees after hatching. Then it hibernates on stems near the base of the foodplant. In May it starts to feed again, and when fully grown it can be as long as 80 mm. It has hairs which can cause irritation. It is widespread in Europe. The name comes from fleshy "lappets" that hang down around the prolegs. Pupation is in June, in a tough cocoon of brown/grey silk and hairs spun low on the food plant.
Adults emerge in June or July. The wing length is 28 - 42 mm, and the wing span is 56 - 84 mm. The females are larger and darker in colour than the males. They are good fliers and can be seen flying during the day. At rest they are well camouflaged as they look like a bunch of dead leaves.
Both sexes have pectinate antennae, though the female is less pectinate than the male, and they do not have a proboscis. They are generally found among hedgerows and woodland edges. The female emits a sexual attractant pheromone that, to us, smells of charcoal or burnt wood.