| Thick-headed Flies
belong to the Conopidae family,
but certain anatomical features, suggest that they are
closely related to hoverflies. Several species are
excellent wasp mimics and the larvae of this parasitic
family feed internally in bees and wasps. The adults are
nectar feeders, regularly visiting flowers. One Thick-headed Fly (Conops
quadrifasciata) specialises in feeding on bumblebees
- waiting near flowers for a bee to arrive, piercing the
body and quickly depositing an egg inside. The egg
hatches and the larva feed off the abdominal contents of
the bumblebee for about 10 days, effectively hollowing it
out and filling almost the entire abdominal cavity. The
larva pupates inside the bee becoming an adult fly the
next summer. Parasitised bees appear to change the
behaviour and tend to stay outside the nest more than
other workers, often remaining outside even in very cold
weather.
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