Colias eurytheme
In 3 days ~20% in a week ~40%
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 Death Valley National Park on a given day, based on 6 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 91st most-seen of the 108 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.
June–July and October
In those months about 20% of wildlife watchers report an Orange Sulphur in Death Valley National Park on a given day, against under 5% in April–May, August–September and November–February, the lowest months.
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.
9th of 16
Of the 16 parks where we can rate Orange Sulphur sightings, Death Valley National Park ranks 9th at about 10%. The best odds are in Point Pelee National Park (Canada, about 20%), Badlands National Park (United States, about 20%) and Sequoia and Kings Canyon National Parks (United States, about 10%).
Same family: Pieridae
The closest relatives of the Orange Sulphur that you can see in Death Valley National Park (family Pieridae, Whites, Yellows, and Sulphurs) are Checkered White (about 10%) and Becker's White (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Orange Sulphur is recorded against all the insects logged in Death Valley National Park (6 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.
