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Family Overview
This common and widespread group includes roughly 80 North American species in 9 genera. Larvae can be readily identified, as this is the only mayfly group with gills absent on abdominal segment 2. They tend to be found in lotic-erosional or depositional habitats, often among the rooted aquatic plants, moss, root masses, or woody debris. They usually are poor swimmers, swimming with a floppy motion, and instead sprawl or cling to the plants or other substrates in their habitat. The family has a variety of feeding strategies, differing among species, including collector-gatherers, scrapers, some shredders of detritus or algae, and even one predator. When a larva is disturbed it sometimes raises its tail over its head like a scorpion, possibly as an adaptation to fend off predators; however, they cannot sting. After emergence, adults sometimes swarm atypically high, even above tree tops. This group is one of the most important for the fly-fishing community, with at least 30 different species being used as models for tied flies.
Characteristics
POLLUTION TOLERANCE
Mid-Atlantic: up to 4
Upper Midwest: 1 - 5
Midwest: 1.2 - 2.9
Southeast: 0.1 - 5.4
0 = least tolerant, 10 = most tolerant
FEEDING HABITS
Collector / Gatherer
Scraper / Grazer
Shredder / Detritivore
Shredder / Herbivore
MOVEMENT
Clinger
Sprawler
Swimmer
Diagnostic Characters
+ Expanded Character List
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.