Vespula pensylvanica
In 3 days ~20% in a week ~30%
Vespula pensylvanica, the western yellowjacket (western yellow jacket), is a Nearctic species of wasp in the genus Vespula. It is native to regions of North America, largely in areas with northern temperate climates. Its reproductive behavior is constrained by cold weather, which successfully reduces the number of western yellowjackets in cold months. However, in the absence of cold weather, this wasp's population can explode. The western yellowjacket has become particularly invasive in the Hawaiian Islands, resulting in their label as a major pest.
V. pensylvanica was originally named by de Saussure in 1857; it falls into the subgenus Paravespula, within Vespula. Paravespula consists of 11 species, which have been divided into four groups on the basis of morphological differences. V. pensylvanica falls into the same group as V. germanica. With the exception of Allovespula, the subgenera recognized within Vespula are natural groups. The separation of Rugovespula and Paravespula appears to be monophyletic; however, this is not well established.
The western yellowjacket shares the basic yellow and black pattern with other... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Channel Islands National Park | 🇺🇸 United States | |
| 2 | Zion National Park | 🇺🇸 United States | |
| 3 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States | |
| 4 | Grand Canyon National Park | 🇺🇸 United States | |
| 5 | Yosemite National Park | 🇺🇸 United States | |
| 6 | Olympic National Park | 🇺🇸 United States | |
| 7 | Great Bear Rainforest | 🇨🇦 Canada | |
| 8 | Rocky Mountain National Park | 🇺🇸 United States | |
| 9 | Joshua Tree National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Salt Lake City | 🇺🇸 United States | |
| 2 | Sacramento | 🇺🇸 United States | |
| 3 | Calgary | 🇨🇦 Canada | |
| 4 | Denver | 🇺🇸 United States | |
| 5 | San Francisco | 🇺🇸 United States | |
| 6 | Vancouver | 🇨🇦 Canada | |
| 7 | Edmonton | 🇨🇦 Canada | |
| 8 | Portland | 🇺🇸 United States | |
| 9 | Seattle | 🇺🇸 United States | |
| 10 | San Diego | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Western Yellowjacket sighting in Rocky Mountain National Park on a given day, based on 10 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 119th most-seen of the 191 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.
June, August and October–November
In those months about 10% of wildlife watchers report a Western Yellowjacket in Rocky Mountain National Park on a given day, against under 5% in July, September and December–May, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Western Yellowjacket sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
8th of 9
Of the 9 parks where we can rate Western Yellowjacket sightings, Rocky Mountain National Park ranks 8th at about 10%. The best odds are in Channel Islands National Park (United States, about 20%), Zion National Park (United States, about 10%) and Sequoia and Kings Canyon National Parks (United States, about 10%).
GBIF citizen-science records
It is estimated from how often the Western Yellowjacket is recorded against all the insects logged in Rocky Mountain 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.
