A vocabulary of landscape — a landscape of words
1367 entries
mayfly
A mayfly spends one to three years underwater as a nymph and a day or two in the air. The adult has no working mouthparts and does not feed. It emerges, molts once more in the open air, mates in a swarm over the water, lays, and dies. It is the only insect that molts again after acquiring functional wings, which is why anglers deal with two adult stages: the dun and, after the final molt, the spinner.
Etymology
The English name is for the month the great hatches occur in Britain, though the group as a whole emerges across the whole warm season. The scientific order name is Greek for short-lived winged things, built on the same root as ephemeral.
Notes
The dun and spinner distinction is on this site under dun. Mayfly nymphs need clean, well-oxygenated water and are among the standard indicator groups for river quality: count the mayfly, stonefly, and caddis species in a kick sample and you have a usable measure of a river without a single chemical test. A large hatch can cover bridges and roads and shows on weather radar.