I've seen Ceratina taking an interest in the hollow ends of some of the sticks in that container:


This wasp is likely the same specimen that flies around plants and examines them; photographed before, on rose. I didn't recognize her because of the arched abdomen. I thought it must be another species, with different anatomy. She wouldn't be searching for bee brood on foliage out in the open, would she?

Perhaps she would be seen on foliage as a result of seeking sustenance in the form of dew droplets or honeydew. Incidentally, Grotea appear to be somewhat unique among the ichneumonids in that the larvae consume multiple larvae of Ceratina and also eat some of the pollen or bee bread with which the Ceratina cells have been provisioned.

The original 1905 "Entomological News" article by S. Graenicher describing in great detail the info Bob Carlson commented on above is quite enjoyable to read, and can be found here.

And thanks, R. Berg, for posting your great images of Grotea ovipositing, and of the Ceratina above, and the cross-section of the twig with the bee (and perhaps larval chambers?). It's so neat how BugGuide allows us all to see such special finds, and illuminates the life history of these creatures.

I've been enchanted by this species since seeing it about a year ago across the bay from you. I just posted a series of a male:



More to come of a female soon. (And I know what you mean about them being difficult to photograph!)

Graenicher's article interested me for its style. Current scientific writing doesn't read like that. The tone is personal and homely, and the sentences are elegantly constructed. In those days, I believe, scholars in any field were likely to have studied Latin and Greek, and it shows in their English.

Apparently, in 1905, no one knew how these wasps oviposited!

Those were my sentiments exactly when I read the article!

Compare the style of modern technical articles about molecular genomics and cladistics with the natural history writings of John Muir :-)

(Clicking error here...meant to edit comment above!)