Black Horse Fly vs Yellow Swarming Fly

Side-by-side species comparison

Attribute Black Horse Fly Yellow Swarming Fly
Scientific Name Tabanus atratus Thaumatomyia notata
Order Diptera Diptera
Family Tabanidae Chloropidae
Size 20-28 mm 2-2.5 mm
Habitat Farmland Grasslands
Diet Blood Feeders Predators
Regions Eastern United States from the Great Plains to the Atlantic coast Europe
Conservation Least Concern Least Concern

Black Horse Fly

A very large entirely black horse fly and one of the biggest flies in North America. Females are persistent blood-feeders that can harass livestock and humans during summer months.

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Did You Know?

Its larvae are aquatic predators that live in muddy pond bottoms and can take up to two years to complete development.

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.