Pachysphinx occidentalis
In 3 days ~20% in a week ~30%
Pachysphinx occidentalis, the big poplar sphinx, is a moth of the family Sphingidae. The species was first described by Henry Edwards in 1875. It lives throughout Canada and the United States. The habitat consists of riparian areas and suburbs.
The wingspan is 130–150 mm. There are two color forms, a pale form with yellow-brown forewings, which are dark gray in the dark form. The lines and bands are well defined. The upperside of the hindwing has a crimson patch covering varying amounts of the wing, and two dark lines which do not form a distinct triangle.
There are two generations per year in southern Arizona with adults on wing from May to September. Farther north, there is one generation per year with adults on wing from June to August. The larvae feed on cottonwood Populus and Salix species. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Zion National Park | 🇺🇸 United States | |
| 2 | Grand Canyon National Park | 🇺🇸 United States | |
| 3 | Big Bend National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Las Vegas | 🇺🇸 United States | |
| 2 | Salt Lake City | 🇺🇸 United States | |
| 3 | Denver | 🇺🇸 United States | |
| 4 | Sacramento | 🇺🇸 United States | |
| 5 | San Diego | 🇺🇸 United States | |
| 6 | Los Angeles | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Western Poplar Sphinx sighting in Big Bend National Park on a given day, based on 7 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 221st most-seen of the 329 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.
February, April–May and October–November
In those months about 10% of wildlife watchers report a Western Poplar Sphinx in Big Bend National Park on a given day, against under 5% in March, June–September and December–January, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Western Poplar Sphinx sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Among the best
Of the 3 parks where we can rate Western Poplar Sphinx sightings, Big Bend National Park ranks 3rd at about 10%, level with the leaders once rounded. The best odds are in Zion National Park (United States, about 10%) and Grand Canyon National Park (United States, about 10%).
Same family: Sphingidae
The closest relatives of the Western Poplar Sphinx that you can see in Big Bend National Park (family Sphingidae, Sphinx Moths) are White-Lined Sphinx (about 30%), Five-Spotted Hawk Moth (about 10%) and Falcon Sphinx (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Western Poplar Sphinx is recorded against all the insects logged in Big Bend National Park (7 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.
