Urophora cardui
In 3 days ~10% in a week ~30%
Urophora cardui or the Canada thistle gall fly is a fruit fly which, contrary to its common name, is indigenous to Central Europe from the United Kingdom east to near the Crimea, and from Sweden south to the Mediterranean. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Wadden Sea National Park | 🇩🇪 Germany |
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Manchester | 🇬🇧 United Kingdom | |
| 2 | Birmingham | 🇬🇧 United Kingdom | |
| 3 | Toronto | 🇨🇦 Canada | |
| 4 | London | 🇬🇧 United Kingdom | |
| 5 | Denver | 🇺🇸 United States | |
| 6 | Portland | 🇺🇸 United States | |
| 7 | Montreal | 🇨🇦 Canada | |
| 8 | Chicago | 🇺🇸 United States | |
| 9 | Baltimore | 🇺🇸 United States | |
| 10 | Saint Petersburg | 🇷🇺 Russia |
Rare
Under 5% of wildlife watchers report a Thistle Stem Gall Fly sighting in Wadden Sea National Park on a given day, based on 10 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 422nd most-seen of the 818 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
July to September
In those months about 10% of wildlife watchers report a Thistle Stem Gall Fly in Wadden Sea National Park on a given day, against under 5% in October to June, the lowest months.
Between 1 and 4 pm
Across all the parks we cover, that three-hour window holds the most Thistle Stem Gall Fly sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Wadden Sea National Park, in our data
Wadden Sea National Park is the only park on Wallace's Line with enough records to rate Thistle Stem Gall Fly sightings: under 5% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the Thistle Stem Gall Fly is recorded against all the insects logged in Wadden Sea National Park (10 verified sightings from 2019 to 2026), 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.
