Holly leaf miner

Found on various species of holly (Ilex), particularly the common European Holly (Ilex aquifolium) in gardens and woodlands.

Larvae (maggots) are herbivores that feed exclusively on the internal leaf tissue (mesophyll) of holly plants, creating visible tunnels or mines.

The female fly lays eggs in the leaf midrib; once hatched, the larva mines the leaf throughout the winter. They pupate within the leaf and emerge as adults in late spring or early summer.

Primarily an aesthetic pest causing pale or brown blotches on foliage; they rarely kill the plant. They provide a food source for specialized parasitic wasps and some birds like blue tits.