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Guide to New Zealand's freshwater invertebrates
Rallidens mayfly nymphs have a torpedo-like body form, fringed caudal filaments (“tails”), short antennae and double abdominal gills (the inner gill being fringed).
They are most common in stony or gravelly, bush covered streams
Rallidens larvae may feed on biofilm (algae and other microorganisms) and plant detritus on the streambed.
Abundances of Rallidens suggest good habitat and water quality conditions, especially if other mayfly or stonefly groups are abundant. They have tolerance values of 9 (hard bottom sites) and 3.9 (soft bottom sites).