June 27th – This post was inspired by top Pelsall geezer Matt Drew, who spotted a different clump of these fellows and posted a pic on Facebook last week, inspiring me to look out for them.

These delightfully spiky caterpillars are the larvae of the beautiful peacock butterfly. They really are rather impressively hostile-looking, but cute at the same time – I spotted them in a nettle bed at the top of Shire Oak Hill, near the old quarry there.

In summer, the adult female peacock will lay between 200 and 500 eggs at the very top of a stinging nettle in direct sunlight. 10 days later they’ll hatch, and the emerging caterpillars will spin a communal web-tent out of silk (see the top picture) which they’ll live in until large enough to leave; they live and grow in clumps at the top of nettles, and as they grow, they may move from nettle to nettle in a patch together as a group, before pupating separately.

They’re easy to spot as a dark infestation at the tops of the tallest nettles in a nettle bed. 

Male peacock butterflies are very territorial, and can often be seen attempting to chase away birds that may be coming near their selected nettle patch.

I’m glad I found some – and thanks again to Matt for the inspiration to look.