Among the wasps nesting in the bee hotel nestblocks is Passaloecus. P. gracilis has been observed nesting and possibly other species as well. Many P. corniger males are active on them but it remains to be confirmed if the females of that species are among the nesting females.
A female of one of the parasites of the former species, Poemenia collaris, seems to be busy parasitising what appears to be a Passaloecus nest judging by the resin that is visible at the edge of the entrance. The open entrance and the resin holding debris indicate this is an old nest that has been reused, which suits the behaviour of at least P. corniger.
References1 Nederlands Soortenregister