SPECIES ID / Invertebrates

True Flies

Blackfly Larvae


  • 165 species in North America

Order:Diptera (True flies)
Family:Simulidae (Black flies)

Identification Tips:

• Vase shaped body with circular attachment structure at base.
• Two brushy appendages protruding from head.
• 2 Fleshy prolegs on body just below head.

Life History:

• Found only in flowing water (all current speeds)
• Attach to rock, wood or other submerged objects
• Filter feeders: collect drifting organic material from the current with brush-like appendages protruding from their heads. They periodically flick the brushes into their mouths to clean off accumulated food.
• Pupate in tent like structure attached to rocks

Very SensitiveSomewhat SensitiveFacultativeSomewhat TolerantVery Tolerant
Pollution IndicatorHigh abundance is a reliable indicator of moderate organic pollution

Primary Information Source:
Voshell, J. Reese. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald and Woodward Publishing Company. Blacksburg, Virginia.