Wasp Wednesday: Parancistrocerus perennis

One of the hymenopterists I am most indebted to is Dr. Matthias Buck at the Royal Alberta Museum in Edmonton. Amazingly, from the two images presented here, he was able to identify this little mason wasp as Parancistrocerus perennis.

I imaged this one at Cape May Point State Park in New Jersey on October 18, 2010. The species ranges from southern Ontario to Florida, and west to the Mississippi River. Southern specimens are in the subspecies anacardivora and frequently sport reddish markings along the side of the first abdominal segment. They are not large, with a wing length of only 6-8 millimeters.

The female wasps, when not nectaring on wildflowers, go hunting for caterpillars of the families Coleophoridae and Tortricidae. Tortricids are known as “leafrollers” because that is exactly what the little caterpillars do: they roll leaves of their host plant, binding them with silk such that they don’t unroll. This makes for a snug little shelter where the moth larva can feed in peace. Except when the wasp comes knocking, of course. How the wasp ever succeeds at getting to these caterpillars and subduing them escapes me. Even if the caterpillar is exposed by the wasp, it can quickly execute a “bungy jump,” leaping off the leaf on a thread of silk it can climb back up on once danger has passed. Oh, and it is not like coleophorids are easy pickings, either. They are the “casebearer” moths, the caterpillars living inside a case of their own hardened fecal matter.

Nevertheless, the little Parancistrocerus perennis perseveres, paralyzing caterpillars with her sting and stocking them inside hollow twigs. Each female divides the ready-made tunnel into several cells, prepared one at a time from the bottom up. After piling up enough caterpillars, she lays a single egg on the last victim. She seals the cell by crafting a partition of sand that she glues together with her saliva. Then she repeats the process.

You can make the wasp equivalent of an apartment dwelling for this species and other solitary wasps (and bees) by drilling holes of various diameters into a block of wood and posting it in a south-facing sheltered spot at least three feet off the ground. You could even bundle a bunch of old sumac twigs, the tree species preferred by several solitary twig-nesters.

Want more information on this species and other members of the family Vespidae? Dr. Buck and his associates have created an online identification guide to the nearctic Vespidae, and I’ll offer the species page for Parancistrocerus perennis as an example of their diligent work.

For blueprints on how to make artificial nests, visit this page at Gardens for Wildlife, or the many other web pages on this subject to be found in a Google search. You can also find videos on YouTube that show both how to build such “bee boxes,” but also the insects themselves coming and going from those pre-fab condos.