Last week I was pleased to see the first vapourer moths of the year on the wing along the public footpath by the silt lagoons and later, Beach Hut volunteer Dave Roberts recorded one at the start of the visitor trails. A favourite of mine, they have some interesting aspects to their lifecycle….
The males fly during the day and at night and so can be seen on warm days during the flight period of July – October, starting slightly later in the north. They occur in one protracted generation throughout this period. The males are a bright orange colour, making them obvious in flight and are worth looking at closely if they land to appreciate the colouration, with dark cross bands and white spot near the trailing edge of the forewings.
The females on the other hand are totally different. They are completely flightless, possessing only vestigial wings. Grey/brown in colouration, they have a large, swollen abdomen and spend pretty much all of their imago (adult) lifestage in the vicinity of the pupal case that they hatched out of. The female releases pheromones that attract the flying males and after mating they lay their eggs on the empty pupal case, where they (the eggs) will overwinter.
And it’s not just the imago insects that are interesting. The larvae are stunning, with a dark coloured body, they are covered in tufts of long hairs of different colours and lengths. Four of these hair tufts, located towards the larva’s head end and cream in colouration are thought to mimic the eggs of parasitic wasps. These wasps lay their eggs on the larva, which then hatch and eat the moth larva alive, before pupating themselves inside or on the eaten body of the moth. Mimicking the eggs of these wasps is thought to provide protection for the moth by fooling the wasp into thinking that the larva has already been parasitised.
Vapourer moth larva. Roger Tidman (rspb-images.com)
Larval foodplants include many broadleaved trees and shrubs, therefore allowing the species to occur in a range of habitats. They are common and widespread throughout much of the UK.