Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Guide to New Zealand's freshwater invertebrates

Swimming mayfly ( Rallidentidae : Rallidens )

Diagnostic features

Rallidens mayfly nymphs have a torpedo-like body form, fringed caudal filaments (“tails”), short antennae and double abdominal gills (the inner gill being fringed).

Typical habitats

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.

Indicator value

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).