Fly (Stonefly) Order: Plecoptera
Common name: Stonefly
Stoneflies are a small group of aquatic insects in the order Plecoptera. Stoneflies usually live in areas with running water. There are some 3,500 species are found worldwide, except Antarctica. There are over 100 species described in New Zealand. All genera and species are endemic to New Zealand apart from the genus Notonemoura, which is shared with Australia although the species are endemic to each country.
Stoneflies as adults have a life-span of 2 to 3 weeks. They have two pairs of wings, which are transparent and fold flat over their backs when at rest. They have simple mouthparts with chewing mandibles. Their antennae are long and are multiple-segmented. Their eyes are large and compounded. Their legs are robust and terminate with claws. Both nymphs and adults have long, paired tail filaments.
Stoneflies are univoltine (having one generation a year). Mating takes place on the ground and the female lays her eggs in fresh water. The carnivores’ nymphs when hatched live in water.
They remain in the nymphal form for one to four years, depending on the species. They undergo from 12 to 33 moults before emerging at a specific times of the year to exit the final nymph skin to become terrestrial adults.
All species of Plecoptera are intolerant of water pollution and their presence in a stream or still water is usually an indicator of good or excellent water quality.
A stonefly Megaleptoperla grandis collected from the Tauranga Water Supply stream area which consistently gets some of the best water quality rating in New Zealand.