Adelges tsugae
In 3 days ~10% in a week ~20%
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.
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| # | 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 |
Rare
Under 5% of wildlife watchers report a Hemlock Woolly Adelgid sighting in New York City on a given day, based on 55 verified sightings from GBIF citizen-science data. It is the 361st most-seen of the 1623 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Hemlock Woolly Adelgid in New York City on a given day, so our monthly data shows no clear season.
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.
6th of 6
Of the 6 cities where we can rate Hemlock Woolly Adelgid sightings, New York City ranks 6th at under 5%. The best odds are in Boston (United States, about 10%), Philadelphia (United States, under 5%) and Washington (United States, under 5%).
Same order: Hemiptera
The closest relatives of the Hemlock Woolly Adelgid that you can see in New York City (order Hemiptera, True Bugs, Hoppers, Aphids, and allies) are Spotted Lanternfly (about 40%), Large Milkweed Bug (about 20%) and Oleander Aphid (about 10%), 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 New York City (55 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.
