Polycaon stoutii
In 3 days ~10% in a week ~20%
Polycaon stoutii, the black polycaon or Stout's branch borer, is a species of woodboring beetle in the Bostrichidae family. It is found in North America in British Columbia, the Pacific Coast states, and Arizona, but has spread elsewhere due to the shipping of wood products.
Polycaon stoutii breeds in hardwoods. The female bores into the wood and lays its eggs in a tunnel. Usually, these host trees are dead or dying, but they are reported to bore into healthy ones as well. Recorded host trees include redwood, coast live oak, maple, manzanita, madrone, California laurel, sycamore, hickory, mahogany, ash, and various fruit trees. Infestation can occur before the trees have been harvested or in a lumberyard.
Larvae develop inside the wood for at least a year, but can remain there for over twenty years before emerging as adults. They are known for occasionally emerging from wooden furniture. Adults are 10-23 mm in length. They are cylindrical, hairy, and black. Their heads are slightly downturned.
Polycaon stoutii can be distinguished from the related P. granulatus by the antennae having 11 segments and the 2nd and 3rd tarsal segments being... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Yosemite National Park | 🇺🇸 United States |
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Los Angeles | 🇺🇸 United States | |
| 2 | San Francisco | 🇺🇸 United States | |
| 3 | San Diego | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Stout's Hardwood Borer sighting in San Francisco on a given day, based on 43 verified sightings from GBIF citizen-science data. It is the 242nd most-seen of the 737 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 Stout's Hardwood Borer in San Francisco on a given day, so our monthly data shows no clear season.
Between 7 and 10 pm
Across all the parks we cover, that three-hour window holds the most Stout's Hardwood Borer sightings with a recorded time, and about half of them come between 6 am and 6 pm: it is seen both by day and at night.
Among the best
Of the 3 cities where we can rate Stout's Hardwood Borer sightings, San Francisco ranks 2nd at under 5%, level with the leaders once rounded. The best odds are in Los Angeles (United States, under 5%).
Same order: Coleoptera
The closest relatives of the Stout's Hardwood Borer that you can see in San Francisco (order Coleoptera, Beetles) are Asian Lady Beetle (about 20%), Seven-Spotted Lady Beetle (about 20%) and Convergent Lady Beetle (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Stout's Hardwood Borer is recorded against all the insects logged in San Francisco (43 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.
