Yellow Swarming Fly vs Thick-headed Fly

Side-by-side species comparison

Attribute Yellow Swarming Fly Thick-headed Fly
Scientific Name Thaumatomyia notata Physocephala rufipes
Order Diptera Diptera
Family Chloropidae Conopidae
Size 2-2.5 mm 8-14 mm
Habitat Grasslands Underground
Diet Predators Parasitoids
Regions Europe Europe
Conservation Least Concern Least Concern

Yellow Swarming Fly

A tiny yellow fly famous for forming enormous hibernation aggregations in buildings, sometimes numbering millions. Larvae are predatory on root aphids in grassland.

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Did You Know?

Can form hibernation clusters of millions in attic spaces, with individual aggregations weighing several kilograms.

Thick-headed Fly

A wasp-mimicking fly that parasitizes bumblebees by injecting eggs into them mid-flight.

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Did You Know?

Infected bumblebees bury themselves in soil where the fly larva pupates.