Oncopeltus fasciatus
In 3 days ~20% in a week ~50%
Oncopeltus fasciatus, known as the large milkweed bug, is a medium-sized hemipteran (true bug) of the family Lygaeidae. It is distributed throughout North America, from Central America through Mexico and the Caribbean to southern areas in Canada. Costa Rica is the southern limit of its range. It inhabits disturbed areas, roadsides, and open pastures. Due to this widespread geographic distribution, the large milkweed bug exhibits varying life history trade-offs depending on the population location, including differences in wing length and other traits based on location.
Adults can range from 11 to 12 mm in length and have a red/orange and black X-shaped pattern on their wings underneath the triangle that is typical to hemipterans. This feature makes the bug easily seen, acting as an aposematic warning to predators. O. fasciatus exhibits Müllerian mimicry and is noxious to predators. The ventral side of the fourth abdominal segment bears a black band in the male and two black spots in the female. Juveniles are born mostly red with black antennae and a few black spots, throughout growth the black spots are developed as well as wing pads. The eggs are bright orange... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Shenandoah National Park | 🇺🇸 United States | |
| 2 | Point Pelee National Park | 🇨🇦 Canada | |
| 3 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 4 | El Vizcaíno Biosphere Reserve | 🇲🇽 Mexico | |
| 5 | Grand Canyon National Park | 🇺🇸 United States | |
| 6 | Padre Island National Seashore | 🇺🇸 United States | |
| 7 | Saguaro National Park | 🇺🇸 United States | |
| 8 | Zion National Park | 🇺🇸 United States | |
| 9 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States | |
| 10 | Merritt Island National Wildlife Refuge | 🇺🇸 United States | |
| 11 | Channel Islands National Park | 🇺🇸 United States | |
| 12 | Big Bend National Park | 🇺🇸 United States | |
| 13 | Cumbres de Monterrey National Park | 🇲🇽 Mexico | |
| 14 | Everglades National Park | 🇺🇸 United States | |
| 15 | Joshua Tree National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Chicago | 🇺🇸 United States | |
| 2 | Washington | 🇺🇸 United States | |
| 3 | Baltimore | 🇺🇸 United States | |
| 4 | New York City | 🇺🇸 United States | |
| 5 | Philadelphia | 🇺🇸 United States | |
| 6 | Detroit | 🇺🇸 United States | |
| 7 | Ciudad Juárez | 🇲🇽 México | |
| 8 | Dallas | 🇺🇸 United States | |
| 9 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 10 | Austin | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Large Milkweed Bug sighting in Saguaro National Park on a given day, based on 32 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 71st most-seen of the 354 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 50%, if each day is a fresh chance.
February to November
In those months about 10% of wildlife watchers report a Large Milkweed Bug in Saguaro National Park on a given day, against under 5% in December and January, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Large Milkweed Bug sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
7th of 15
Of the 15 parks where we can rate Large Milkweed Bug sightings, Saguaro National Park ranks 7th at about 10%. The best odds are in Shenandoah National Park (United States, about 20%), Point Pelee National Park (Canada, about 10%) and Great Smoky Mountains National Park (United States, about 10%).
Same family: Lygaeidae
The closest relatives of the Large Milkweed Bug that you can see in Saguaro National Park (family Lygaeidae, Seed Bugs) are Southern Small Milkweed Bug (about 10%), Charcoal Seed Bug (about 10%) and Small Milkweed Bug (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Large Milkweed Bug is recorded against all the insects logged in Saguaro National Park (32 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.
