Osmia caerulescens
In 3 days ~10% in a week ~30%
Osmia caerulescens, the blue mason bee, is a species of solitary bee from the family Megachilidae. It has a Holarctic distribution extending into the Indomalayan region, although its presence in the Nearctic may be due to human-assisted introduction.
Females of Osmia caerulescens are 10–11 mm in length, dark blue-black in color, with a metallic sheen, and sparsely covered with brown hairs with those on the abdomen forming a narrow, dense, flattened band on the hind margin of each of the segments. The dense brush of pollen-collecting scopae on the underside of the abdomen is jet black. The males are slightly smaller, 9mm, more slender in build, distinctly metallic green and clothed with pale hairs.
O. caerulescens occurs in a wide variety of habitats, including woodland and private gardens. O. caerulescens uses a variety of pre-existing cavities for nesting, such as insect burrows in dead wood, drilled borings in wooden blocks, hollow stems, drilled borings in pithy stems, burrows created by other insects in the ground, abandoned cells in exposed nests of other aculeates, cavities in banks, holes and crevices in walls, and glass tubes. The... Wikipedia →
| # | Park | Country | Daily sighting probability |
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More parks will be added in future updates.
With luck
About 10% of wildlife watchers report a Blue Mason Bee sighting in London on a given day, based on 44 verified sightings from GBIF citizen-science data. It is the 492nd most-seen of the 1504 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.
April to June
In those months about 10% of wildlife watchers report a Blue Mason Bee in London on a given day, against under 5% in July to March, the lowest months.
Among the best
Of the 6 cities where we can rate Blue Mason Bee sightings, London ranks 2nd at about 10%, level with the leaders once rounded. The best odds are in Warsaw (Poland, about 10%).
Same genus: Osmia
The closest relatives of the Blue Mason Bee that you can see in London (genus Osmia, Mason Bees) are Red Mason Bee (about 10%) and European Orchard Bee (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Blue Mason Bee is recorded against all the insects logged in London (44 verified sightings), 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.
