Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Guide to New Zealand's freshwater invertebrates

Marsh flies ( Sciomyzidae : Sciomyzidae )

Diagnostic features

The Sciomyzidae is another one of the less common families of true flies in our fresh waters. Their larvae are maggot-like, but the body is characterised by a very “bumpy” outline. There is no visible head, but there is a spiracular disc (breathing structure) at the end of the abdomen.

Typical habitats

Sciomyzid larvae are most likely to be found in slow flowing weedy streams, wetlands, ponds or lakes.


The sciomyzids are predators, preying primarily on molluscs, including sphaeriid bivalves and snails.

Indicator value

The ability of sciomyzids to tolerate slow-flowing, low-oxygen habitats allows them to live in waters of relatively poor quality. They therefore have low tolerance values of 3 for both hard and soft bottom sites.