Emperor moth (Saturnia pavonia).
Open moorland and heaths.
A large, colourful moth. The male is reddish-brown and has large feathery antennae. The female is larger, greyer in colour and has thinner antennae. Both the male and female have markings on their wings like large eye-spots and this makes them look a bit like a cat’s face from a distance. This could be to make the moth look as fierce as possible to scare off birds.
The male is active during the day and flies swiftly over the moor in search of females. Females are less active during the day and appear at dusk. They attract males by releasing a scent which can be detected by the male’s antennae over a mile away. Several males will often gather around a female until one mates with her.
Eggs are laid in May and June and hatch into small, furry, black caterpillars. These feed on heather, bramble and blackthorn. The caterpillars moult several times and gradually get bigger. Fully grown caterpillars are green with black stripes, dotted with yellow or purple warts out of which grow tufts of hairs.
In late summer the caterpillar stops feeding and attaches itself to a twig or strong shoot of heather using a silk thread. It then spins a dark brown cocoon around itself. The entrance to the cocoon is funnel-shaped with the narrow end outwards to prevent predators from entering. The caterpillar remains inside the cocoon over winter and gradually pupates (changes into a moth). When a caterpillar pupates, most of the cells in its body break down and then slowly grow again in a completely different shape such as a moth or a butterfly. The pupal stage lasts over the winter and the moth emerges the following spring.
Emperor moths are common throughout Britain, and are most common on upland moors where there is plenty of heather. Many pupae are killed by parasitic wasps, and heather burning probably kills many more over-wintering pupae, but the long-term survival of emperor moths is not threatened in this area.
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