Mountain Prosimulium vs Autumn Horse Fly

Side-by-side species comparison

Attribute Mountain Prosimulium Autumn Horse Fly
Scientific Name Prosimulium mixtum Tabanus autumnalis
Order Diptera Diptera
Family Simuliidae Tabanidae
Size 2-4 mm 16-22 mm
Habitat Mountains Heathland
Diet Omnivores Blood Feeders
Regions North America Europe, North Africa, Western Asia
Conservation Least Concern Least Concern

Mountain Prosimulium

An early-season black fly of cold mountain streams in North America. Larvae develop in small headwater streams during late winter and early spring.

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Did You Know?

Adults emerge so early in spring that they are often the first biting flies encountered by hikers each year.

Autumn Horse Fly

A large greyish horse fly active in late summer and autumn. It has striking green-banded eyes and a persistent biting habit.

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Did You Know?

It is one of the few horse fly species that remains active well into October.