A couple of weeks ago I noticed ‘something’ dark and rough, like crumpled ladybird exuvia perhaps, seemingly stuck to thistle stems across the Great Chalfield estate. When I looked more closely these ‘exuvia’ actually moved (albeit slowly) and were very difficult to remove from the plants. Moreover I soon noticed that there were insects attached to them still – with peculiar branched spines and looking somewhat like greenish woodlice.
I had absolutely no idea what they were, but the internet has (as usual) come to the rescue and it turns out that what I’m seeing are the larvae of Tortoise Beetles. Which species I’ve not absolutely determined yet but it seems likely – given how widespread the species is – that they are Green Tortoise Beetles Cassida rubiginosa which typically feed on thistles. It turns out that these larvae typically carry bits of fecal matter (and perhaps of previously shed exo-skeletons) on ‘anal prongs’ which curve back over the body to disguise themselves from predators. Internet accounts state that when disturbed the larvae will often wave this shield at would be predators, but I’ve not noticed this myself so far…
The following images aren’t very good (I admit) but now that I know what these peculiar little specks of detritus really are I’ll go back and check them out again. Thistles (which a number of UK Cassida species favour) are common in the conservation headlands here, but I’ve not so far seen any adult Tortoise Beetles. I’ll be looking out for them now that I know that they’re breeding here and hopefully identify them properly then.
All photos copyright Charlie Moores/Talking Naturally 2012