Image Credit: Kentish Plumber
Thick-headed flies (Conopidae) – parasites of pollenivores. Conopid flies are internal parasites of adult bees and ants. There have been attempts to use them as biocontrol for fire ants. There are about 5 common genera in the PNW. Conopids attack their target prey in mid-air, grabbing them with their legs, depositing an egg on the neck, and letting them go again all within a split-second.
All thick-headed flies share the same distinctive body shape, with the under-curved abdomen. Most are small (4-6 mm, like on the left), the mid-sized red Myopa is about 6-8 mm, and the bumblebee parasite (Physocephala) on the right is 10-15 mm long.