Lois Connington and I have been watching bamboo tubes fill up rapidly these past few weeks in our Bee Wall, but until just now we have not known the identity of the new residents. This afternoon we were preparing a square for bamboo in the upper quadrant of the bee wall when Lois noticed a blue-black wasp collecting dirt from a nearby patch of exposed ground. The wasp immediately flew into a bamboo tube and deposited her load. After watching the wall for several minutes, we saw three more wasps carrying loads of dirt, fiber and caterpillars to their respective tubes. I was finally able to snap a few shots of the large, beautiful black-and-cream Monobia quadridens, known commonly as the “Four-toothed Mason Wasp”.
These gentle giants are common to the Eastern United States, and they often make use of preexisting carpenter bee tunnels in which to lay eggs and raise young from late spring to early fall. In our case they are using bamboo tubes of various diameters that we provided in the Bee Wall. The females build individual cells for each larva that are separated by mud partitions. Typically, female larvae are in the back and male larvae towards the entrance, since the latter have a shorter development time. The cells are provisioned with paralyzed butterfly or moth larvae, which become the food of the developing wasp. One such butterfly larvae was not very thoroughly paralyzed when I observed a female carrying it into the tunnel and it turned around and began to crawl back out!
We are so excited to see these new pollinators in our bee wall! Look for them sipping nectar on asters, button bush and other late-summer wildflowers. Remember, these are docile wasps, unlike their defensive cousins, the Bald Face Hornets. If you have any doubt about identity, the Four-toothed Mason wasp has an entirely black head, whereas the Bald Face Hornet has a creamy mask.