Dasineura crataegi
In 3 days ~10% in a week ~20%
Dasineura crataegi, the hawthorn button-top gall-midge, is a dipteran gall-midge. It causes the hawthorn button-top gall, which develops in the terminal shoots of common hawthorn, Crataegus monogyna Jacq., Midland hawthorn C laevigata (Poir.) DC and their hybrid, C × media Bechst. Synonyms are Perrisia crataegi and Cecidomyia crataegi (Winnertz, 1853).
The midge induces stunted and distorted rosettes in the host by inhibiting the elongation of the shoot; the rosette is formed from many (8 to 40 or more) slightly thickened and deformed leaves with reduced petioles. Many of the leaves have small green or red ligulate excrescences or projections. The midge larvae are of an orange-red colour.
The gall is occasionally found on isolated plants, but infestation is more commonly in hedges, with the new growth resulting from hedge cutting being the site of high density populations. The rosettes stand out prominently against the sky. Old galls persist and new shoots grow from unaffected buds lying well behind the terminal bud.
Adults emerge from pupae in the ground beneath the shrub and the terminal bud infestations start in March or April; the... Wikipedia →
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Rare
Under 5% of wildlife watchers report a Hawthorn Button-Top Midge sighting in Paris on a given day, based on 6 verified sightings from GBIF citizen-science data. It is the 743rd most-seen of the 916 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 a Hawthorn Button-Top Midge in Paris on a given day, so our monthly data shows no clear season.
Among the best
Of the 2 cities where we can rate Hawthorn Button-Top Midge sightings, Paris ranks 2nd at under 5%, level with the leaders once rounded. The best odds are in London (United Kingdom, under 5%).
GBIF citizen-science records
It is estimated from how often the Hawthorn Button-Top Midge is recorded against all the insects logged in Paris (6 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.
