There are 18 species of this common and widespread genus known in North America; in the East, adults of some of these are called Hendricksons or Sulphurs by fly fishers. Larvae inhabit all types of streams, where they cling to the substrate while collecting small particles of organic matter or scraping diatoms and algae and other biofilm from rocks and other surfaces.
Southeast: 0 - 4
Upper Midwest: 1 and higher
Midwest: 2.9 and higher
Collector / Gatherer
Scraper / Grazer
Scraper / Grazer
Widespread (east of the Rocky Mtns.)
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Order: Wings developing in wing pads. Mouthparts suitable for chewing. Gills present on tops and sides of abdomen. Segmented legs present. One tarsal claw per leg. Usually with 3 tails (sometimes 2).
Family: Gills on abdominal segment 1 rudimentary or absent. Abdominal segment 2 without gills. Gills on abdominal segments 3 (if present) and 4–7 have two layers: a top layer that is oval and plate-like and a bottom layer that is multi-lobed; in preserved specimens these gills lying in paired dorsal depressions and camouflaged, not readily seen by novices. Abdominal terga often with paired tubercles. Mature larvae 5–15 mm long, not including tails.
Genus: Maxillary palps well developed. Forefemora thicker than foretibiae, lacking conspicuous anterior tubercles, spurs, or spines, but almost always with some bristle-like or robust setae on top. Gills arising from posterior margins of abdominal segments 3-7. Main part of ventral lamella of each abdominal gill 6 entire, not cleft. Caudal filaments (tails) with many interfacing fine setae (at least 3 or 4 on a side of each segment).