Hyphantria cunea
In 3 days ~10% in a week ~30%
The fall webworm (Hyphantria cunea) is a moth in the family Erebidae known principally for its larval stage, which creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods in the late summer and fall. It is considered a pest but does not harm otherwise healthy trees. It is well known to commercial tree services and arboriculturists. Fall webworms are an invasive species in East Asia.
The adult fall webworm has a wingspan of approximately 30 mm and is generally white-colored, although some individuals may have dark-colored marks. The moth is native to North America, ranging from Canada to Mexico and has been introduced into other continents. Introduced to what was formerly Yugoslavia in the 1940s (firstly recorded in 1949), it now has occupied probably its entire range in Europe from France to the Caspian Sea in the east as well as penetrated into Central Asia: Turkmenistan (from 1990 to 1993), Uzbekistan (Fergana valley from 1996 to 1997), Kyrgyzstan, and southeastern Kazakhstan. It was also introduced into Japan in 1945 and has adjusted its number of generations per year since its arrival. It spread into China, southern... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Congaree National Park | 🇺🇸 United States | |
| 2 | Shenandoah National Park | 🇺🇸 United States | |
| 3 | Acadia National Park | 🇺🇸 United States | |
| 4 | Point Pelee National Park | 🇨🇦 Canada | |
| 5 | Big Cypress National Preserve | 🇺🇸 United States | |
| 6 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 7 | Cape Breton Highlands National Park | 🇨🇦 Canada | |
| 8 | Grand Teton National Park | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Fall Webworm Moth sighting in Portland on a given day, based on 42 verified sightings from GBIF citizen-science data. It is the 139th most-seen of the 507 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
August and September
In those months about 10% of wildlife watchers report a Fall Webworm Moth in Portland on a given day, against under 5% in October to July, the lowest months. Those are among Portland's driest months, with about 40 mm of rain a month against 250 mm in December.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Fall Webworm Moth sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
20th of 31
Of the 31 cities where we can rate Fall Webworm Moth sightings, Portland ranks 20th at about 10%. The best odds are in Gwangju (South Korea, about 40%), Seoul (South Korea, about 20%) and Milan (Italy, about 20%).
Same family: Erebidae
The closest relatives of the Fall Webworm Moth that you can see in Portland (family Erebidae, Underwing, Tiger, Tussock, and Allied Moths) are Isabella Tiger Moth (about 20%), Cinnabar Moth (about 20%) and Arctia tigrina (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Fall Webworm Moth is recorded against all the insects logged in Portland (42 verified sightings), 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.
