Andricus curvator
In 3 days ~10% in a week ~20%
Andricus curvator is a gall wasp which forms chemically induced leaf galls on oak trees and has both agamic and sexual generations. Agamic and sexual generations usually form two distinct galls on oak trees, but in the case of A. curvator there are six galls; the sexual generation usually on the leaf, occasionally in a twig or catkin, and the agamic generation in a bud. The wasp was first described by Theodor Hartig, a German biologist, in 1840 and is found in most of Europe.
Adult gall wasps emerge in the spring, from galls formed on the bud the previous year. The spring generation lay eggs usually on a leaf, occasionally on a twig or on catkins and the leaf galls appear soon after the leaves emerge. They are approximately 8 mm, roughly globular and have thin walls with a small inner gall. They often coalesce and can be clustered near the leaf base where they can cause distortion. Galls on a twig cause the twig to bend and it can also occur at the tip. These galls have an interior cavity which can be spherical or oval. A fourth sexual gall can also develop on the base of a catkin stalk and is up to 5 mm diameter. What remains of the catkin is bent 90° and can still... Wikipedia →
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Rare
Under 5% of wildlife watchers report an Oak Curved-Leaf Gall Wasp sighting in Vienna on a given day, based on 17 verified sightings from GBIF citizen-science data. It is the 666th most-seen of the 1406 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.
January and April
In those months about 10% of wildlife watchers report an Oak Curved-Leaf Gall Wasp in Vienna on a given day, against under 5% in February–March and May–December, the lowest months.
5th of 6
Of the 6 cities where we can rate Oak Curved-Leaf Gall Wasp sightings, Vienna ranks 5th at under 5%. The best odds are in Liverpool (United Kingdom, about 10%), London (United Kingdom, about 10%) and Birmingham (United Kingdom, under 5%).
Same genus: Andricus
The closest relatives of the Oak Curved-Leaf Gall Wasp that you can see in Vienna (genus Andricus) are Knopper Gall Wasp (about 10%), Andricus dentimitratus (about 10%) and Andricus caputmedusae (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Oak Curved-Leaf Gall Wasp is recorded against all the insects logged in Vienna (17 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.
