Background

Carcelia iliaca (C. iliaca) is a parasitoid that is associated with Oak Processionary Moth (Thaumetopoea processionea; OPM).

C. iliaca parasitises older, almost full-grown OPM larvae inside or outside OPM nests and then completes its development by overwintering in a spent OPM nest before emerging the following spring.

Identification

C. iliaca:

• resembles a dark grey housefly or bluebottle-shaped fly
• has a body length of approximately eight-10 millimetres
• can be observed running over OPM nests and caterpillars
• can be found in the general vicinity of active OPM nests.

Where C. iliaca is observed on OPM nests, caterpillars may appear agitated.

Images of C. iliaca

Bottom picture: credit The Royal Parks

To request a PDF (non-accessible) version of this field guide, please contact the OPM team.