Turbinate-eyes
Guides
Baetidae
small mayflies, small minnow mayflies
Baetidae is the most species-diverse family of mayflies, comprising approximately 1,000 described species in 110-114 genera worldwide and representing about one-third of all mayfly diversity. Adults are among the smallest mayflies, rarely exceeding 10 mm in length excluding tails, with some species much smaller. The family has a cosmopolitan distribution except for New Zealand and occupies a relatively basal position in Ephemeroptera phylogeny.
Cloeon dipterum
Pond Olive
Cloeon dipterum is a small mayfly species with a Holarctic distribution, widespread across Europe, Asia, and North America. It is the most common mayfly in ponds of the British Isles, occurring in approximately 40% of all ponds and 70% in southern regions. The species is notable for being the only ovoviviparous mayfly in Europe: females retain eggs internally for 10–14 days after mating, and nymphs hatch immediately upon contact with water. Males possess distinctive turbinate eyes—dorsal "turban-shaped" superposition eyes that aid in locating females during mating swarms. The species has been established as a laboratory model for studying insect evolution, development, and ecotoxicology.