Insect life at the fen is reaching peak activity, with soldier beetles covering almost every piece of hogweed, bright yellow longhorn beetles patrolling the thistle flowers and bush crickets lining the wooden edge of sandy wall. This is a good time to keep an eye out for one of Strumpshaw’s best mini-spectacles. Huge numbers small tortoiseshell and peacock caterpillars are currently erupting all over their larval foodplants, and in some cases covering almost every square inch of foliage. At the moment there’s a brilliant example on the nettles just by the first sluice on the fen trail. When we walked past it yesterday almost every plant was heaving with small tortoiseshell caterpillars, eggs and frass (that’s caterpillar poo to me and you) as individuals crawled over each other and stretched out into any empty spaces in search of more leaves to devour.
Small Tortoiseshell Caterpillars. Photo by Ciara Stafford
Small tortoiseshell caterpillars hatch out from their bright green eggs after one to three weeks. They live in groups, and together spin untidy silk webs at the top of nettles which they can retreat to in order to protect themselves from predators. If caught out in the open (I saw them do this when a green bottle fly had the audacity to land on them) the whole group will flick their bodies from side to side in unison to defend themselves. After a month of continuous eating, they will finally disperse to find a suitable place to pupate.
Small tortoiseshell caterpillars in their silk web. Photo by Ciara Stafford
Seeing a nettle patch turned into an insect metropolis highlights the importance of these much maligned plants in maintaining some of our most beautiful butterflies. As well as small tortoiseshells they support the larvae of commas, red admirals, peacocks and painted ladies; so next time you get stung, think of all the good that plant may have done. You might find yourself a little more willing to forgive it.