Subject: Unidentified Beetle found in McCleary, WA
Location: McCleary, WA
August 20, 2012 10:04 pm
We are hoping you may be able to help us identify a beetle we found on our screen door this evening 8/20/2012, in McCleary, WA. It measured approximately 2cm. The antennae were alternating black and white (or at least black and a lighter, contrasting color). The texture of the shell/wings looked very ”pitted”.
Thank you for your help!
Signature: Sarah and Shawn Z
Dear Sarah and Shawn,
Your Longhorned Borer Beetle in the family Cerambycidae is Stictoleptura canadensis, and it goes by the common name Red Shouldered Pine Borer. It is a transcontinental species found in both the east and the west. We have an example of a Red Shouldered Pine Borer in our archives that is colored like your specimen, and we have another example of a Red Shouldered Pine Borer that is colored more like its common name indicates, with red shoulders. BugGuide shows both individuals with red elytra and others with black elytra and red shoulders and the only images of mating pairs of Red Shouldered Pine Borers on BugGuide have the female with the coloration like your individual and the male with red shoulders, however there is no indication on BugGuide that this is sexual dimorphism. To further complicate the picture, there are a few examples of all black Red Shouldered Pine Borers on BugGuide. We are going to contact Doug Yanega and Eric Eaton to see if either of them can explain this variation in coloration.
Doug Yanega explains the color variations
As noted in my field guide, S. canadensis (the eastern subspecies) varies from red-shouldered to completely red elytra, in both sexes. I didn’t investigate other subspecies, but can’t imagine why they wouldn’t also be variable in coloration. There are LOTS of cerambycids with numerous color variants (as opposed to sexual dimorphism), and they’re often sympatric (i.e., genuine variation, rather than geographic differentiation).
Dept. of Entomology
Entomology Research Museum
Univ. of California, Riverside, CA
Thank you so much!!! We thought we had correctly identified it as a female Elderberry Longhorn (Desmocerus auripennis) because it has the same texture on the outer wings and looked nearly identical. The only difference were the antennae, which were verigated (unlike the images of D.auripennis we found).
Would love to know what causes the color variation.
Again, thanks so much for getting back to us! We love your website!
-Sarah and Shawn Z