Once again, I was alerted to this little leafminer by a tweet from Rob Edmunds (@leafminerman), one of the brains behind the British Leafminers website, and I’ve now found it at three local sites where Hart’s-tongue fern (Phyllitis scolopendrium) is plentiful, though it can also be found on a couple of other fern species.

These are the larvae of Psychoides filicivora, a tiny brown moth (you can see the adult on the UK Moths website here), whose larvae munch on the fern fronds and hide away under little ‘nests’ of sporangia on the undersides of the fronds.

There is another very similar moth species that also lives on fern fronds, Psychoides verhuella – so far, I’ve only found P. filicivora – but the British Leafminers website has very good information on both, as well as an excellent side-by-side comparison image of their larvae.