Pictured here is one of numerous large carpenter bees (at least four, seemingly many more) that were frenetically cruising around an old downed tree trunk at mid-day. It was warm and sunny in an open, park-like environment of mixed conifers & chaparral on the flat, wide bottom of Kings Canyon. The location was trail-side at an elevation of ~5100', about a mile east of roads end—just beyond Cedar Grove.

After I noticed that all these bees were repeatedly visiting the same spot under the downed log, I bent down to try to figure out why they were so excited. Each bee would zoom to the same spot and pause for a moment hovering. (At which point I could photograph them!). After inspecting the situation briefly, they'd then zoom off without ever landing. This behavior was repeated over and over by numerous bees.

It seemed the object of their attention was a lifeless form—what appears to be a dark wing(?) and one or two hard to distinguish adjacent blobs, seen to the left of center in the images posted here. These blobs are poorly lit and resolved, and partially obscured within a crevice in the wood and by a piece of dried up California Black Oak leaf. They seemed not to move throughout the time I was present.


I have two hypotheses on what may have been happening here:

1) Perhaps the "object" was a mating pair of carpenter bees. It that case, the pair was remarkably still (at least during the few minutes I observed). And there are more questions: Why were the many inquiring males refraining from landing? Was it due to a sense of xylocopid courtesy? Or perhaps a lack of good spots to alight, maybe even the ferocity of their rival? Perhaps a combination of these and other reasons...the possibilities are manifold.

2) The "object" may have been a dead female bee, perhaps caught by a spider lurking near the entrance to her nest. These are relatively big and powerful bees...so I'd think a spider would have to use the element of surprise to catch one.

In either case, I presume the presence of female xylocopid pheromone emanating from the object was causing the frenetic behavior in the visiting (male?) bees.

At any rate, I'd appreciate any comments that might confirm, correct, or further elucidate my speculations here on this behavior, as I didn't have the presence of mind (or inclination) to poke a stick in there to investigate...and I was already in a rush to catch up with my companions :-) Also, I've been unable to find info on xylocopid mating behavior (or other likely explanations for what I observed here).

As for ID, after studying Hurd(1) and the info on this UC Riverside web page, I'm thinking these are male Xylocopa californica ssp. californica, due to the (subtle) greenish tint of their metasoma, and the pale yellowish pile of their thoraces and first abdominal segments.

For full-size image, click this link.