Emperor moths (Saturnia pavonia) are incredibly beautiful and probably one of my favourite moths of all. Belonging to the same family as silk moths, they are the only member of Saturniidae found in the UK. A few years ago one laid her eggs in a friend’s moth trap which gave us a great opportunity to rear them and use them in our educational talks.
The caterpillars are very striking and large at around 6cm long. You can really see how their banding and white spots would provide excellent camouflage against their favourite food plant, heather. They are common across Britain but most often found on moorland habitat from May-August. Once fully grown, the caterpillars spin a papery but strong cocoon which helps protect against parasitic insects. Inside, the caterpillars pupate and overwinter before emerging as adults the following April.
The moth shown in the photograph is a male – you can tell from its feathery antennae used to detect pheromones produced by the female. Males also tend to be smaller and more colourful than the large females (up to 10cm wingspan), which are often grey-blue in shade. Males fly by day, detecting the pheromones produced by the inactive female. They are often mistaken for small tortoiseshell butterflies as they flutter across the heather. Up close however they are unmistakeable, being the only British large moth with eyespots on all four wings.