Taxonomic group
Family: Empididae
Diagnostic features
The empidid flies are common in many New Zealand streams, but they can be easily overlooked due to their small size. There are different forms of larvae, but the most common form has a maggot-like body with a fully retracted head, and with 7 pairs of caterpillar-like prolegs along the abdomen. The pupae of some empidids are surrounded by radiating threads.
Typical habitats
Empidid larvae are found in many stream types, but they can be particularly common amongst algal mats on stony streambeds.
Feeding
We don’t know much about the diet of New Zealand empidids, but the larvae of overseas species are often predators and/or scavengers.
Indicator value
- Hard bottom: 3
- Soft bottom: 5.4
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
Empidid larvae can be common in farmland streams with some nutrient enrichment. They have low to moderate tolerance values of 3 (hard bottom sites) and 5.4 (soft bottom sites).