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Single gill mayfly (Deleatidium)

Taxonomic group

Leptophlebiidae: Deleatidium

Diagnostic features

Deleatidium mayfly nymphs have a flattened body form, single leaf-like gills and a wide labrum (top “lip”).

Typical habitats

Deleatidium larvae are the most abundant invertebrates in many fast-flowing, stony-bottom streams with cool and well aerated water, especially in the South Island.


Leptophlebiid mayflies feed by scraping diatom algae and other organic matter from stone surfaces.

Indicator value

  • Hard bottom: 8
  • Soft bottom: 5.6

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

High abundances of Deleatidium suggest good habitat and water quality conditions, especially if other mayfly or stonefly groups are abundant. Deleatidium has tolerance values of 8 (hard bottom sites) and 5.6 (soft bottom sites).