Some photographs of Chelostoma philadelphi, the most common guest at my mason bee hotel in past years. Approximately 7 mm in length and all black unless covered in pollen. Seems to prefer nest holes that are 1/8″ in diameter. In looking at photographs online they seem to show up on a variety of flowers (perhaps with preference for asters), but females are reported (Sedivy et al. 2008) to collect only Philadelphus pollen for use in nest provisions for her brood.
If you’re fond of hole-nesting bees and wasps, please join the new “Bee and Wasp Hotels” project on iNaturalist.org to document the guests and hangerson that arrive at your hotel.
Currently the most photographed visitor is the four-toothed mason wasp (Monobia quadridens). But also plenty of mason bees as well as parasites looking for mason bees. There has also been a slug sighting (don’t ask).
If this sounds fun but you don’t have a hotel, here are my thoughts on building one.
