’Tis the time of the larvae, in this case, the larvae of the Peacock butterfly (Aglais io).
According to Life Cycles of British & Irish Butterflies, a female Peacock lays her eggs in batches of about 400 in the centre of a patch of nettles growing in a sheltered position that enjoys full sun. After about two weeks, the Peacock larvae/caterpillars hatch and begin their journey to adulthood.
As they munch on the nettles, they grow, and as they grow, they need to moult their skins. They do this four times, each stage known as an instar, before they pupate. The process takes about 30 days in total, and each of the five instars looks a little different.
During last Friday’s walk, I was lucky enough to find big colonies of larvae in two different places, and both groups had larvae of the third, fourth and fifth instars, all feeding together. In the photo above, the brownish caterpillars are third instar, the darker caterpillars with spines and spots are fourth instar, and the large caterpillar on the right of the image is fifth instar.
Not surprisingly, I got a few nettle stings getting these photos but it was worth it. As some of the largest caterpillars looked very close to pupation, I’ll revisit one of these sites this week to see if I can locate any pupas.