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Swimming mayfly (Ameletopsis)

Taxonomic group

Ameletopsidae: Ameletopsis

Diagnostic features

Ameletopsis mayfly nymphs have a wide, skull-like head, and their caudal filaments (“tails”) are fringed on each side.

Typical habitats

Ameletopsis larvae are most abundant in bush-covered, gravelly streams with cool and well aerated water.


They are predators, feeding on other freshwater invertebrates.

Indicator value

  • Hard bottom: 10
  • Soft bottom: 10

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Ameletopsis are not often found in high abundance, but they are indicative of good habitat and water quality, especially if other mayfly or stonefly groups are abundant. Ameletopsis has the highest tolerance value of 10 for both hard and soft bottom sites.