Istocheta aldrichi
In 3 days ~20% in a week ~40%
Istocheta aldrichi or winsome fly is a species of fly in the family Tachinidae. Originally from Japan, it has been introduced in North America in 1922 as a biocontrol to combat the Japanese beetle (Popillia japonica). It is established in northeastern North America, including Canada and the USA. Larvae pupate inside the host beetle after hatching from an egg laid on the beetle's pronotum. Historical host range catalogues and recently collected crowdsourced data suggests that this fly is highly specific to Japanese beetle and probably does not attack other beetle species. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Acadia National Park | 🇺🇸 United States |
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Montreal | 🇨🇦 Canada | |
| 2 | Minneapolis [Saint Paul] | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Winsome Fly sighting in Acadia National Park on a given day, based on 14 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 171st most-seen of the 405 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.
July and August
In those months about 10% of wildlife watchers report a Winsome Fly in Acadia National Park on a given day, against under 5% in September to June, the lowest months.
Between 9 am and noon
Across all the parks we cover, that three-hour window holds the most Winsome 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 Acadia National Park, in our data
Acadia National Park is the only park on Wallace's Line with enough records to rate Winsome Fly sightings: about 10% of wildlife watchers there report one on a given day.
Same order: Diptera
The closest relatives of the Winsome Fly that you can see in Acadia National Park (order Diptera, Flies) are Margined Calligrapher (about 20%), Eastern Calligrapher (about 20%) and Common Drone Fly (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Winsome Fly is recorded against all the insects logged in Acadia National Park (14 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.
