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 →
| # | Park | Country | Daily sighting probability |
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More parks will be added in future updates.
Rare
Under 5% of wildlife watchers report a Hawthorn Button-Top Midge sighting in London on a given day, based on 23 verified sightings from GBIF citizen-science data. It is the 724th 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.
September and October
In those months about 10% of wildlife watchers report a Hawthorn Button-Top Midge in London on a given day, against under 5% in November to August, the lowest months.
Yes
Of the 2 cities where we can rate Hawthorn Button-Top Midge sightings, London has the highest daily chance: under 5%. Next come Paris (France, 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 London (23 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.
