Eurosta solidaginis
In 3 days ~20% in a week ~30%
The goldenrod gall fly (Eurosta solidaginis), also known as the goldenrod ball gallmaker, is a species of fly native to North America. The species is best known for the characteristic galls it forms on several species in the Solidago, or goldenrod, genus. The fly's eggs are inserted near the developing buds of the plant. After hatching, the larvae migrate to an area below the plant's developing buds, where they then induce the plant's tissues to form into the hardened, bulbous chamber referred to as a gall. E. solidaginis’s interactions with its host plant(s) and insect, as well as avian, predators have made it the centerpiece of much ecological and evolutionary biology research, and its tolerance of freezing temperatures has inspired studies into the anti-freeze properties of its biochemistry.
Eurosta solidaginis is in the order Diptera and the family Tephritidae. The Tephritidae are commonly referred to as fruit flies, a common name they share with the Drosophilidae family. The goldenrod gall fly was first put into the genus Eurosta by D. W. Cocquillet in 1910. Two subspecies exist: E. solidaginis subsp. solidaginis and E. solidaginis subsp. fascipennis, distinguished... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Elk Island National Park | 🇨🇦 Canada | |
| 2 | Great Smoky Mountains National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Montreal | 🇨🇦 Canada | |
| 2 | Toronto | 🇨🇦 Canada | |
| 3 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 4 | Calgary | 🇨🇦 Canada | |
| 5 | Chicago | 🇺🇸 United States | |
| 6 | Houston | 🇺🇸 United States | |
| 7 | Washington | 🇺🇸 United States | |
| 8 | Edmonton | 🇨🇦 Canada | |
| 9 | Boston | 🇺🇸 United States | |
| 10 | New York City | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Goldenrod Gall Fly sighting in Great Smoky Mountains National Park on a given day, based on 32 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 334th most-seen of the 822 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 30%, if each day is a fresh chance.
January
In that month about 20% of wildlife watchers report a Goldenrod Gall Fly in Great Smoky Mountains National Park on a given day, against under 5% in February, April–May, August, October and December, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Goldenrod Gall Fly sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 2 parks where we can rate Goldenrod Gall Fly sightings, Great Smoky Mountains National Park ranks 2nd at about 10%, level with the leaders once rounded. The best odds are in Elk Island National Park (Canada, about 10%).
Same order: Diptera
The closest relatives of the Goldenrod Gall Fly that you can see in Great Smoky Mountains National Park (order Diptera, Flies) are Eastern Calligrapher (about 20%), Margined Calligrapher (about 10%) and Ocellate Gall Midge (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Goldenrod Gall Fly is recorded against all the insects logged in Great Smoky Mountains National Park (32 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.
