Searching for leafmines on thistles is not for the faint-hearted, writes she with multi-punctured fingers. But it has been worth every drop of blood to find these mines (and I must be a masochist, as, having found them in one place, I then went determinedly searching in other locations – two successes so far, which I’m rather pleased about as there are very few records in south Wales).
The larvae of the moth Coleophora peribenanderi, also known as the Pale Thistle case-bearer (you can see the adult on UK Moths here), builds itself a tube-like case to live in and ventures out of said case to munch happily on the leaves of whichever species of thistle its mother laid her eggs on (in the three I’ve found so far, Creeping thistle). The marks this feeding makes on the plant’s leaves are quite distinctive but, to clinch the identification, you need to look under the leaf and find the case.
Interestingly, the larva feeds up for a couple of months, from July to September, then suspends its development (the scientific word is diapause, a new one for me) through the winter until either feeding up a bit more in April or passing straight to pupation in May. Fascinating stuff!