This week I have been collecting some data for the Agromyzidae recording scheme, run by a member of the Yorkshire Naturalists Union that I am becoming more involved with. As it is close to Christmas, the group put out a request for records of the holly leaf mining fly, Phytomyza ilicis. This is one of few insects that can use tough holly leaves as a food source.
Females lays their eggs in the holly leaf in early Spring when leaves tend to be younger and softer. Larvae emerge from the eggs and tunnel along the leaf veins, creating a "mine". After a period of feeding, the larva turns into a pupa, then later an adult fly emerges from the pupa and leaf mine via a small hole, less than a millimetre in diameter, on the leaf surface. The larva may not make it to the adulthood as it may be parasitised by the eggs of a wasp – which devour it - or it may be eaten by by a blue tit. If this happens, there may be evidence that the leaf mine has been pecked at/ripped open and the insect removed.
The holly leaf miner is common throughout Europe but appears under-recorded, so hopefully my efforts will help contribute some useful data.
I went for several walks around my neighbourhood and found signs of the leaf miner on many of the trees/bushes. They did seem more prevalent on the older, more mature holly trees. Young bushes or those that had been trimmed (eg. within hedgerows) seemed to be less affected by Phytomyza ilicis.
Sightings can be reported using iRecord (please submit a photograph and your location).
