Shore flies (Ephydridae)

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.

Shore fly [Ephydridae]. Larva with paired respiratory siphons. Image: Stephen Moore Image — Shore fly Ephydridae. Larva with paired respiratory siphons. Image: Stephen Moore

Shore fly [Ephydridae] pupa. Image: Stephen Moore Image — Shore fly Ephydridae pupa. Image: Stephen Moore

Typical habitats

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

Feeding

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).