Andricus grossulariae
In 3 days ~20% in a week ~40%
Andricus grossulariae is a gall wasp species inducing agamic acorn cup galls on oak tree acorn cups and sexual phase galls on catkins. Acorn cup galls develop as a chemically induced distortion of the growing acorn cups on oak trees, caused by gall wasps which lay eggs within the tissues of the acorn cup. The sexual phase appears on catkins as rounded structures (6 mm × 3–4 mm) possessing a characteristic point, and are covered with fine hairs when young. The galls, shiny and hard, turn red in colour, and then black or dark purple.
The asexual or parthenogenetic phase, about 10 mm across, develops on acorn cups of English oak Q. robur and sessile oak Q. petraea. The galls, formed of flattened projections, often enclose the immature acorn. The galls first appear pink in colour and as they mature they turn red, then green and finally brown during their development. Previously this asexual stage was known as Andricus mayri (Wachtl).
Although normally distinctive, the asexual... Wikipedia →
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More parks will be added in future updates.
With luck
About 10% of wildlife watchers report an Andricus grossulariae sighting in London on a given day, based on 98 verified sightings from GBIF citizen-science data. It is the 321st most-seen of the 1504 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
April–May and August–November
In those months about 10% of wildlife watchers report an Andricus grossulariae in London on a given day, against under 5% in June–July and December–March, the lowest months.
Among the best
Of the 6 cities where we can rate Andricus grossulariae sightings, London ranks 2nd at about 10%, level with the leaders once rounded. The best odds are in Liverpool (United Kingdom, about 10%).
Same genus: Andricus
The closest relatives of the Andricus grossulariae 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 grossulariae is recorded against all the insects logged in London (98 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.
