Yellow Swarming Fly vs Small-headed Fly

Side-by-side species comparison

Attribute Yellow Swarming Fly Small-headed Fly
Scientific Name Thaumatomyia notata Ogcodes pallidipennis
Order Diptera Diptera
Family Chloropidae Acroceridae
Size 2-2.5 mm 4-8 mm
Habitat Grasslands Grasslands
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.

Small-headed Fly

A round-bodied fly with a tiny head whose larva parasitizes spiders from the inside.

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Did You Know?

The first-instar larva attaches to a passing spider and burrows inside to feed.