Bombus bifarius
In 3 days ~30% in a week ~60%
Bombus bifarius, the two-form bumblebee, is a species of eusocial bumblebee of the subgenus Pyrobombus. B. bifarius inhabits mountainous regions of western North America, primarily the states of Colorado and Utah. Its common name refers to a historical artifact, in that it was believed that this species had a color polymorphism, with a red-tailed nominate form and a black-tailed nearcticus form present in the species. This polymorphism has recently been shown to belong instead to a cryptic sister species, Bombus vancouverensis, that occupies almost the entirety of the range of what was formerly classified as bifarius; true bifarius only has a red form, so it is not "two-formed" at all.
Bombus bifarius was first described by Ezra Townsend Cresson in the 1878 Proceedings of the Academy of Natural Sciences of Philadelphia. It is a member of the order Hymenoptera and the family Apidae, which also includes orchid bees, honey bees, and bumblebees. It was long believed that B. bifarius expressed varying color patterns, with the two most observed being the nominate and nearcticus color patterns. Red-tailed specimens classified as B. bifarius are found from Colorado... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Rocky Mountain National Park | 🇺🇸 United States |
More parks will be added in future updates.
With luck
About 10% of wildlife watchers report a Colorado Black-Notched Bumble Bee sighting in Rocky Mountain National Park on a given day, based on 54 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 21st most-seen of the 191 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 60%, if each day is a fresh chance.
July and August
In those months about 20% of wildlife watchers report a Colorado Black-Notched Bumble Bee in Rocky Mountain National Park on a given day, against under 5% in October to April, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Colorado Black-Notched Bumble Bee 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 Rocky Mountain National Park, in our data
Rocky Mountain National Park is the only park on Wallace's Line with enough records to rate Colorado Black-Notched Bumble Bee sightings: about 10% of wildlife watchers there report one on a given day.
Same genus: Bombus
The closest relatives of the Colorado Black-Notched Bumble Bee that you can see in Rocky Mountain National Park (genus Bombus, Bumble Bees) are Hunt's Bumble Bee (about 10%), Nevada Bumble Bee (about 10%) and White-Shouldered Bumble Bee (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Colorado Black-Notched Bumble Bee is recorded against all the insects logged in Rocky Mountain National Park (54 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.
