Pond Olive Mayfly
A while ago I was asked questions about Olives here on the blog, so finally thought I'd add something you might find useful for clarrification.
The Pond Olive Mayfly (latin name Cloeon dipterum) is a common and abundant species. The nymphs can be found in a wide range of environments including quiet pools and margins of rivers, in nutrient-enriched ponds, or in the shallow water of large still waters. If observerd it swims in short darting bursts, or can be easily seen climbing amongst weeds and submerged vegetation.
Emergence of the adult takes place at the surface during daylight hours and at dusk. Males in this species are less common as the eggs can develop without fertilisation. When males do occur they swarm in large numbers during the afternoon or dusk. Unusually for mayflies, the female of this species can rest for up to 0ne to two weeks following mating, then laying up to 1200 fully developed eggs onto the water surface where they directly hatch and the young nymphs swim awayimmediately.
There can be two or more generations a year. The later generation will overwinter in its nymphal stage and emerges as adults in the spring. Adults are generally found between May and October, but in warm weather they may also be found in other months.