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Phylum Arthropoda
Class Insecta
Order Ephemeroptera
Family Isonychiidae
Common Name Brushed Legged Mayfly
Distinguishing Characteristics
  • Forelegs with a double row of long setae
  • Gills oval and present on abdominal segments 1-7
  • Long hairs along the margins on caudal filaments
Additional Pictures

     There are 17 species and 1 genera of Isonychiidae found throughout North America. Larval and adults range in size from 8-17 mm and can be cound in rivers with swift to moderate currents. Categorized as collectors and filter feeders; algae, diatoms, and detritus are common sources of food. The organism filters the water using brush-like hairs on their forelegs.

     Isonychiidae cling to substrate with their middle and hind legs and hold their forelegs in the current to collect small particles in the water. They then consume the material collected on their hairs. These mayflies are good swimmers, but they spend most of the time clinging to the substrate. The rows of hairs on the tails help these mayfly larvae swim by functioning as a paddle.

  • Video: Isonychiidae swimming, gill aeration, and avoidance of other organisms
Additional Links



Merritt, R W., K W. Cummins, and M B. Berg. An Introduction to the Aquatic Insects of North America. Dubuque, Iowa: Kendall/Hunt Company, 2008.