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Taxonomic group

Family: Psychodidae

Diagnostic features

Psychodid flies have small larvae that are easily distinguished by the combination of a non-retractile head, a respiratory siphon at the tip of the tail, and many small sclerotised (hardened and pigmented) plates along the length of the abdomen.

Typical habitats

Psychodid larvae can be found along stream margins, amongst decaying vegetation, and sometimes amongst “sewage fungus” growths in polluted waters.


Psychodids eat decomposing organic matter, probably mostly rotting vegetation, associated decomposer microbes and aquatic algae.

Indicator value

  • Hard bottom: 1
  • Soft bottom: 6.1

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

Psychodid larvae can be found in good quality streams, but they can also thrive in quite polluted streams. Their ability to live in “clean” and polluted waters is reflected by the wide ranging tolerance values of 1 (hard bottom sites) and 6.1 (soft bottom sites).