Nesameletus ornatus (Eaton, 1882)

REDUCED NZ-Ento-Soc-Insect-Playing-Cards_Swimming-mayfly

Common name: Swimming mayfly, piriwai

Order: Ephemeroptera   Family: Nesameletidae

Habitat: Live in clean freshwater streams. Predominantly in grassland streams in the South Island

Mayflies spend the first part of their lives as swimming larvae in freshwater streams, more specifically in grassland streams in the South island for this species. They spend a year in rivers feeding on algae and other plant materials and are sometimes known as “the grey darter” to trout fishermen.

Along with stoneflies, mayflie larvae or “nymphs” only live in unpolluted streams. For this reason, they are a useful tool for judging how clean a river is and in New Zealand this measure is called the “Macroinvertebrate community index”.

After a year, during the summer, they climb out of the water to complete their final moult. As adults, mayflies have wings but no mouths which means that they have limited time to find a mate and for females to find a slow part of the stream to lay eggs in. This is why members of the mayfly family are called “ephemeropterans”. “Ephemeroptera” comes from the greek “ephemeros” meaning short lived or for a day and this is also where we get the word “ephemeral” from.