Bee flies

Most bee flies are parasites. Their larvae develop on or inside the larvae of various other groups of insects.

The females often lay their eggs in an underground nest near the host. The newly hatched larvae then have to move to become parasitic on the host that will serve as their food source. The subsequent larvae stages are immobile: they stay either inside (endoparasites) or on the outside of (ectoparasites) their host.

Most of the larvae feed by attaching their mouthparts to the host’s body (often a larva) in order to aspirate its contents.

A number of bee fly species are parasites of the larvae of nest-dwelling bees and wasps. To emerge from these shelters, the insects in the pupal stage use their stiff protuberances to drill their way out. The adults then emerge.