Stigmella lemniscella

A leaf-miner on elm, it needs care to distinguish from S. ulmivora.  In this species, the larvae are yellow, rather than green, and vacated mines have the exit hole on the upperside of the leaf, rather than the underside.  This is the commonest of the three Stigmella species mining elm, and can no doubt be found in all areas of the county where elm is common, perhaps being absent from areas where elm is largely absent, such as parts of the Levels and the more barren, treeless areas of inland Exmoor.  Feeding on elm in hedgerows as well as large trees, it appears to have remained widespread and common despite the effects of Dutch Elm Disease.