Andricus inflator
In 3 days ~10% in a week ~20%
Andricus inflator is a species of gall-forming wasps, in the genus Andricus, which has a sexual and an asexual generation, producing two different galls. The wasp was named by the German biologist Theodor Hartig, in 1840 and is found in Europe.
Like many oak gall wasps, there are two generations per cycle, with one sexual and one asexual, each creating different galls. In spring, the sexual gall is a swelling at the tip of the twig which can be up to 15 mm across. The interior cavitity is long and narrow and at the bottom is an egg-shaped inner gall, containing the larval gall wasp. Old galls persist and can have new shoots growing from them. They are green at first, later becoming the same colour as the twig. The wasps emerge in the summer and after mating, females from the sexual gall lay their eggs on a bud, especially on buds sprouting straight from the trunk. The resulting asexual gall is a small, green, egg-shaped swelling up to 6 mm across and is surrounded by bud scales. Each gall contains a single larva {according to Chinery) or more (according to Plant Parasites of Europe), can be found from September to November and, as it matures, turns brown... Wikipedia →
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Rare
Under 5% of wildlife watchers report an Andricus inflator sighting in London on a given day, based on 8 verified sightings from GBIF citizen-science data. It is the 1300th 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 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report an Andricus inflator in London on a given day, so our monthly data shows no clear season.
Among the best
Of the 2 cities where we can rate Andricus inflator sightings, London ranks 2nd at under 5%, level with the leaders once rounded. The best odds are in Vienna (Austria, under 5%).
Same genus: Andricus
The closest relatives of the Andricus inflator that you can see in London (genus Andricus) are Knopper Gall Wasp (about 20%), Oak Marble Gall Wasp (about 20%) and Ram's Horn Gall Wasp (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Andricus inflator is recorded against all the insects logged in London (8 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.
