So far, in my recent posts on leaf mines, I’ve only covered a few of the many micro moths whose larvae make mines in leaves. But many fly species also inhabit leaves in their larval stage, and today’s post is about one of those, Phytomyza agromyzidae.
You will probably never see the tiny adult fly (and, in fact, I haven’t even been able to find an illustration of one online, though this Wiki page shows an example of one member of the Agromyzidae fly family, which will give you a general idea.) but, anytime between July and November, you should be able to find its larvae’s leaf mines, as it’s probably widespread in Britain (though under-recorded, so if you do find some, please record your sighting).
The mines I’ve found have all been on the leaves of Dogwood (Cornus sanguinea), though it is known to mine other species of Cornus. They’re gallery mines (i.e. forming corridors), long and meandering through the upper side of the leaf surface, and almost completely filled with frass (i.e. poo).
The UK Fly Mines website provides more detailed information on this, and the many other types of leaf mines you can find in Britain.