Colias eurytheme
In 3 days ~40% in a week ~70%
Colias eurytheme, the orange sulphur, also known as the alfalfa butterfly and in its larval stage as the alfalfa caterpillar, is a butterfly of the family Pieridae, where it belongs to the lowland group of "clouded yellows and sulphurs" subfamily Coliadinae. It is found throughout North America from southern Canada to Mexico.
Other members of this lineage including the common or clouded sulphur (C. philodice) and C. eriphyle and C. vitabunda, which are often included in C. philodice as subspecies. Hybridization runs rampant between these, making phylogenetic analyses exclusively utilizing one type of data (especially mtDNA sequences) unreliable. Therefore, little more can be said about its relationships, except that it is perhaps closer to C. (p.) eriphyle than generally assumed, strengthening the view that the latter should be considered a valid species.
The orange sulphur's caterpillars feed off various species in the pea family (Fabaceae) and are usually only found feeding at night. Occasionally this species multiplies to high numbers, and can become a serious pest to alfalfa (Medicago sativa) crops. The parasitoid wasp, Cotesia medicaginis can be used as a biocontrol agent against the caterpillars. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Point Pelee National Park | 🇨🇦 Canada | |
| 2 | Badlands National Park | 🇺🇸 United States | |
| 3 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States | |
| 4 | Joshua Tree National Park | 🇺🇸 United States | |
| 5 | Yosemite National Park | 🇺🇸 United States | |
| 6 | Grand Canyon National Park | 🇺🇸 United States | |
| 7 | Shenandoah National Park | 🇺🇸 United States | |
| 8 | Big Bend National Park | 🇺🇸 United States | |
| 9 | Death Valley National Park | 🇺🇸 United States | |
| 10 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 11 | Channel Islands National Park | 🇺🇸 United States | |
| 12 | Zion National Park | 🇺🇸 United States | |
| 13 | Saguaro National Park | 🇺🇸 United States | |
| 14 | Rocky Mountain National Park | 🇺🇸 United States | |
| 15 | Acadia National Park | 🇺🇸 United States | |
| 16 | Yellowstone National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Dallas | 🇺🇸 United States | |
| 2 | Austin | 🇺🇸 United States | |
| 3 | San Antonio | 🇺🇸 United States | |
| 4 | Sacramento | 🇺🇸 United States | |
| 5 | Denver | 🇺🇸 United States | |
| 6 | Toronto | 🇨🇦 Canada | |
| 7 | Chicago | 🇺🇸 United States | |
| 8 | San Luis Potosí | 🇲🇽 México | |
| 9 | Baltimore | 🇺🇸 United States | |
| 10 | Philadelphia | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report an Orange Sulphur sighting in Sequoia and Kings Canyon National Parks on a given day, based on 23 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 29th most-seen of the 161 insects we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
June to August
In those months about 20% of wildlife watchers report an Orange Sulphur in Sequoia and Kings Canyon National Parks on a given day, against under 5% in October to April, the lowest months. Those are among Sequoia and Kings Canyon National Parks's driest months, with about 25 mm of rain a month against 190 mm in January.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Orange Sulphur sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
3rd of 16
Of the 16 parks where we can rate Orange Sulphur sightings, Sequoia and Kings Canyon National Parks ranks 3rd at about 10%. The best odds are in Point Pelee National Park (Canada, about 20%) and Badlands National Park (United States, about 20%).
GBIF citizen-science records
It is estimated from how often the Orange Sulphur is recorded against all the insects logged in Sequoia and Kings Canyon National Parks (23 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.
