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Taxonomic group

Family: Ephydridae

Diagnostic features

The ephydrids (“shore flies”) are among the less common true flies in our fresh waters. Their larvae have a maggot-like body with a velvety surface texture, and at the end of the abdomen there are two respiratory siphons or (rarely) two black hooks. There is no visible head. Some species have caterpillar-like pseudopods along the underside of the body.

Typical habitats

Ephydrid larvae are found in many stream types including algae-covered streambeds, and some species are common in geothermally heated waters.


Ephydrid larvae are thought to graze on stream biofilms (algae and other microorganisms on submerged surfaces).

Indicator value

  • Hard bottom: 4
  • Soft bottom: 1.4

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

Some ephydrids can be found in polluted or low oxygen waters and as a result they have relatively low tolerance values of 4 (hard bottom sites) and 1.4 (soft bottom sites).