The larval stages are predators or parasitoids of the eggs and larvae of other insects. The adult females usually deposit eggs in the vicinity of possible hosts, quite often in the burrows of beetles, wasps, or solitary bees.
Larvae live parasitically in the nests of various solitary bees and wasps.[2] When the fly larva locates a host larva, it will consume it slowly, greatly increasing in size as it tightly holds onto the host, eventually becoming a pupa and overwintering.[9]
haha yeah, adorable