Green islands

Now the leaves are coming off the trees in droves, it's a good time to look for 'green island' leaf mines on the fallen leaves. These are caused by the mine inhibiting chlorophyll breakdown in the leaf, thus creating a green patch beyond the mine in an otherwise brown or yellow leaf. Some green islands are caused by galls and microfungi, but most are caused by micro-moth leaf mines, so it's a good way to record these species at this time of year.

At Median Farm (Cross Hands) yesterday there were many green island mines in evidence on fallen oak and beech leaves along the track. There were quite a few mines of Ectoedemia subbimmaculella on oak - this species only mines in October and November within these green islands. The larva makes a slit in the lower epidermis of the leaf (usually in a V shape) which distinguishes the mine from other similar species. There are only a few Carms records but it must be very under-recorded. Both the beech-feeding Stigmella species, S. tityrella and S. hemargyrella, were also present.

Ectoedemia subbimmaculella on oak (left) and Stigmella tityrella on beech

There are photos and keys to mines on the excellent leafmines.co.uk website, so it's well worth trying to identify any you find.

George