Just a reminder that searching for the larval stage of leaf-mining species such as the Nepticulids need not be confined to the autumn. A quick search of our garden hawthorn at Westcott, Bucks this afternoon produced the occupied mine illustrated below:
A brief look at the handy mine key for hawthorn (Crataegus) on the UK Leaf-miners web-site (see http://www.leafmines.co.uk/html/mine-guide/hawthorn.htm) tells me that there are seven Nepticulid species to choose from. However, the position of the egg (underside of the leaf, away from the leaf edge), the way the mine has been formed, the colour/dispersal pattern of the frass and the appearance of the larva itself (whitish with a brown head) quickly tells me that this can only be Stigmella hybnerella. It also helps that it is the only one of the seven shown as mining in May, although that's probably the least reliable factor in determining the ID. Anyway, job done and a new species for the garden to boot!