Mayflies (Order: Ephemeroptera)
Mayflies are insects which belong to the Order Ephemeroptera (from the Greek ephemeros = "short-lived", pteron = "wing", referring to the short life span of adults). They are aquatic insects whose immature stage which are called naiad . There are about 40 species of mayfly in New Zealand and all of them are endemic, that is found nowhere else.The adults are short-lived, from a few minutes to a few days depending on the species. They lay their eggs on the surface of lakes or streams, and the eggs sink to the bottom and hatch into naiads which live primarily in streams under rocks, decaying vegetation, or in sediment. and they stay there for about one year. The naiads eat green algae growing on stones and they hide during the day because they are on the diet of many fish.
Mayfly larvae such as Nesameletus have three feather-like tails, which help them swim quickly through the water, and feathery gills along both sides of their bodies that they use to breathe. They are fussy about the water they live in and like cool, clean, well-aerated waters to live in.
Polluted water can cause deformations to their wings and clog up their gills, making it hard for them to fly and breathe. On hatching It often happens that all the mayflies in a population mature at once and for a day or two mayflies will be everywhere, dancing around each other in large groups, or resting on every available surface.
Ameletopsis perscitus (Yellow dun, Sulphur dun)
Photo courtesy of Dean Bell a New Zealand fly fishing guide. http://www.deanbellflyfishing.co.nz