I ran into this dapper beetle about a week and half ago. I wondered if it was attending a masquerade ball or perhaps it was in town as part of a vaudeville performance or magical act out at the Oregon Country Fair.
This beautiful creature is native to the Northwest. As the name suggests, one of its hosts is alder trees, but they will also use ash, willow, oak, and California bay which all can be found at the arboretum. The adult lays eggs singly on a dead or dying branch of a tree. After hatching, the larva will feed under the bark for the next 6 or 7 months. They will then bore into the middle of the branch, pupate and overwinter. In the spring, the adult will emerge and chew its way out. These beetles are essential to breaking down dead or dying wood and recycling the nutrients bank in to the ecosystem.
Its body is 1-1.5 inches in length, not including the antennae.
The pattern of this beetle is a protective measure to evade predators known as disruptive camouflage. The bold stripes break up the form of the beetle especially if it is in dappled sunlight or on lichen growing on the tree.
Oddly enough and for reasons unknown, they are attracted to fresh paint. People reported seeing them show up while painting their house, fence, etc. So keep an eye for them if you have a painting project going on this summer.
Resources
“Banded Alder Borer, or California Laurel Borer.” UC Statewide IPM Program, Agriculture and Natural Resources, University of California, https://ipm.ucanr.edu/home-and-landscape/banded-alder-borer-or-california-laurel-borer/. Accessed 18 July 2026.
"Camoflage 101 – Cryptics." Field Station, University of Wisconsin–Milwaukee, 18 Mar. 2014, https://uwm.edu/field-station/bug-of-the-week/camoflage-101-cryptics/. Accessed 18 July 2026.
Oregon State University Plant Clinic. The Banded Alder Borer. Oregon State University, https://entomology.oregonstate.edu/sites/agscid7/files/entomology/Banded_Alder%20Borer_13.pdf. Accessed 18 July 2026.
"Rosalia Funebris (Banded Alder Borer)." 10,000 Things of the Pacific Northwest, 29 June 2021, http://10000thingsofthepnw.com/2021/06/29/rosalia-funebris-banded-alder-borer/. Accessed 18 July 2026.