EPHEMOROPTERA MAYFLIES
Mayfly Nymphs:
Juvenile mayflies are called ‘nymphs’. Mayfly nymphs live on rocks, vegetation, or in burrows within streams, rivers, lakes, and ponds. They feed on a variety of food sources, usually plants. For most species, maturation takes one year, although some go through multiple generations per year. Once fully grown, environmental cues like temperature, flow, day-length, and weather trigger them to emerge (‘hatch’). Mayfly nymphs range in body size and color but always have only one claw per leg, indistinct thoracic segments, and gills on the abdomen. They usually have three tails.
Clingers
Crawlers
Swimmers
Burrowers
Mayfly Adults:
Mayfly adults are easily identifiable by their upright wings that resemble the sails of a sailboat. When ready to hatch, most mayfly nymphs float from the stream bed to the surface of the water, where they molt in the surface film and take flight. Nymphs of a few large species crawl out on the banks to hatch.
Dun - Subimago
Usually has opaque wings and short tails. Sub-imagos can be seen during the start of a mayfly hatch as they molt and dry their wings on the water surface before taking flight.
Spinner - Imago
Have a darker body, more translucent wings, and longer tails. After mating, the female imagos return to the water to lay their eggs, after which their wings usually lay flat on the water surface, making them hard to see. This is called a ‘spinner fall’.
