Cloeon dipterum
In 3 days ~10% in a week ~30%
Cloeon dipterum is a species of mayfly with a Holarctic distribution. It is the most common mayfly in ponds in the British Isles and the only ovoviviparous mayfly in Europe. Males differ from females in having turbinate eyes.
In common with other members of the genera Cloeon and Procloeon, C. dipterum has a single pair of wings. This is also reflected in the specific epithet dipterum, which is from the Latin di-, meaning two, and the Greek pteron, meaning wing, and in his original description, Carl Linnaeus stated Inferiores alæ vix existunt ("smaller wings hardly present").
The compound eyes of C. dipterum show a striking sexual dimorphism, whereby females have lateral apposition eyes, while the males' eyes have an additional dorsal "turban-shaped" parts that function as superposition eyes. These extra eyes are thought to enable the males to locate isolated females in the mating swarm.
Cloeon dipterum is unusual among mayflies in being ovoviviparous, and is the only ovoviviparous mayfly species known in Europe. Females lay eggs 10–14 days after mating, and the eggs hatch as soon as they hit the water. The larvae can survive for months... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Wadden Sea National Park | 🇩🇪 Germany |
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Madrid | 🇪🇸 Spain | |
| 2 | Rotterdam [The Hague] | 🇳🇱 Netherlands | |
| 3 | Amsterdam | 🇳🇱 Netherlands | |
| 4 | London | 🇬🇧 United Kingdom | |
| 5 | Barcelona | 🇪🇸 Spain | |
| 6 | Liverpool | 🇬🇧 United Kingdom | |
| 7 | Birmingham | 🇬🇧 United Kingdom | |
| 8 | Essen | 🇩🇪 Germany | |
| 9 | Paris | 🇫🇷 France | |
| 10 | Kyiv | 🇺🇦 Ukraine |
No species of the same family or order lives in Wadden Sea National Park, so these are its closest relatives here: other insects.
Rare
Under 5% of wildlife watchers report a Pond Olive sighting in Wadden Sea National Park on a given day, based on 12 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 408th most-seen of the 818 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
May and August
In those months about 10% of wildlife watchers report a Pond Olive in Wadden Sea National Park on a given day, against under 5% in June–July and September–April, the lowest months.
Between 5 and 8 am
Across all the parks we cover, that three-hour window holds the most Pond Olive sightings with a recorded time, and about 7 in 10 of them come between 6 am and 6 pm: it is most active around dawn and dusk.
Only Wadden Sea National Park, in our data
Wadden Sea National Park is the only park on Wallace's Line with enough records to rate Pond Olive sightings: under 5% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the Pond Olive is recorded against all the insects logged in Wadden Sea National Park (12 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
