Orussus thoracicus
Orussus thoracicus is another wasp that is attracted to my spuce stump. The males arrive first in the sping; my earliest iNat observation was this year (2020) was a male on April 16. Upon arrival, they quickly march straight up the trunk for a few feet and march down again, and then repeat.
On May 20, 2018, I saw a mating pair. The male walked down the stump toward the female, who walked up to meet him. She began to furiously beat her white-tipped antennae while he rythmically flicked his abdomen up and daown. Finally, when they nearly met, face to face, the two spun around as though they were doing a square dance. Then the male chased the female around for a few seconds. It didn't seem to me like mating actually took place, but it may have been faster than I could observe.
I have a video of their dance on my phone. I don't know how to include a link to it here, but here's a tweet that I posted about it.
And here’s another video of the Orussus dance. pic.twitter.com/FoQtHQaOag
— Steve Wells (@swells_LQA) January 4, 2022
The male of this species is a bit smaller than the female and has a black abdomen, while the females hs a red one.
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| Male | Female |
IDed on 22 April 23 as Orussus thoracicus by Nathaniel Green, PhD student at Washington State University