Adelges tsugae
In 3 days ~30% in a week ~50%
Adelges tsugae, the hemlock woolly adelgid or HWA, is an insect of the order Hemiptera (true bugs) native to East Asia. It feeds by sucking sap from hemlock and spruce trees (Tsuga spp.; Picea spp.). In its native range, HWA is not a serious pest because populations are managed by natural predators and parasitoids and by host resistance. In eastern North America it is a destructive pest that threatens the eastern hemlock (Tsuga canadensis) and the Carolina hemlock (Tsuga caroliniana). HWA is also found in western North America, where it has likely been present for thousands of years. In western North America, it primarily attacks western hemlock (Tsuga heterophylla) and has only caused minor damage due to natural predators and host resistance. Accidentally introduced to North America from Japan, HWA was first found in the eastern United States near Richmond, Virginia, in 1951. The pest is now found from northern Georgia to coastal Maine and southwestern Nova Scotia as well as areas of western Michigan near the eastern Lake Michigan shoreline. As of 2015, HWA has affected 90% of the geographic range of eastern hemlock in North America.
An adult individual body... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 2 | Shenandoah National Park | 🇺🇸 United States | |
| 3 | Great Bear Rainforest | 🇨🇦 Canada |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Boston | 🇺🇸 United States | |
| 2 | Philadelphia | 🇺🇸 United States | |
| 3 | Washington | 🇺🇸 United States | |
| 4 | Vancouver | 🇨🇦 Canada | |
| 5 | Seattle | 🇺🇸 United States | |
| 6 | New York City | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Hemlock Woolly Adelgid sighting in Shenandoah National Park on a given day, based on 29 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 124th most-seen of the 723 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 50%, if each day is a fresh chance.
February
In that month about 40% of wildlife watchers report a Hemlock Woolly Adelgid in Shenandoah National Park on a given day, against under 5% in March, September and December, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Hemlock Woolly Adelgid sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
2nd of 3
Of the 3 parks where we can rate Hemlock Woolly Adelgid sightings, Shenandoah National Park ranks 2nd at about 10%. The best odds are in Great Smoky Mountains National Park (United States, about 20%).
Same order: Hemiptera
The closest relatives of the Hemlock Woolly Adelgid that you can see in Shenandoah National Park (order Hemiptera, True Bugs, Hoppers, Aphids, and allies) are Spotted Lanternfly (about 50%), Large Milkweed Bug (about 20%) and Acanthocephala terminalis (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Hemlock Woolly Adelgid is recorded against all the insects logged in Shenandoah National Park (29 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.
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