Sweat Fly vs Yellow Swarming Fly

Side-by-side species comparison

Attribute Sweat Fly Yellow Swarming Fly
Scientific Name Hydrotaea irritans Thaumatomyia notata
Order Diptera Diptera
Family Muscidae Chloropidae
Size 5-7 mm 2-2.5 mm
Habitat Farmland Grasslands
Diet Dung Feeders Predators
Regions Europe, North America Europe
Conservation Least Concern Least Concern

Sweat Fly

A small dark fly attracted to perspiration on humans and livestock. It forms dense head-circling swarms in summer that can be extremely annoying.

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Did You Know?

Swarms of these flies can reduce cattle weight gain by causing constant head-tossing behavior.

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.