Paper wasps, like the common aerial yellowjacket I recently mentioned, gather fibers from dead wood and plant stems, mix the fibers with saliva and build water-resistant nests from this material. Unlike the yellowjacket, which builds closed nests, paper wasps build open combs to raise their broods.
The European paper wasp (Polistes dominula) is, as the name implies, an exotic invader that is spreading throughout North America. It was first recorded in Massachusetts in 1968, or 1971 depending on the reference. The exact date is unimportant. Since then the European paper wasp has move westward across the United States. A second invasion began on the West Coast and has been moving to the east. Now this wasp is found almost everywhere in North America.
P. dominula builds open combs in sheltered areas such as the branches of trees, eaves and overhangs of buildings, open pipes and similar locations. European paper wasps seem to prefer areas near humans. A petiole or stalk attaches the comb, open cells facing downward, to the substrate. The wasps secrete a chemical around the petiole that repels ants and keeps the ants from invading the nest. A mature comb can have up to 200 cells and contain 20 to 30 mature adults. European paper wasps are also commonly called umbrella wasps because the comb resembles an opened umbrella. (My imagination is not that active to really see it as an umbrella.)
Semi-social insects, European paper wasps are up to an inch long, slender and narrow-waisted with smoky black wings that are folded lengthwise when the insect is at rest. Native paper wasps often have some red, orange or brown coloration, however, the European paper wasp is yellow and black. They are the only paper wasp with mostly orange antennae.
Generally paper wasps will attack only if they or their nests are threatened. Males do not sting because the stinger is a modified ovipositor, not present in males. In sensitized individuals the sting can cause an anaphalactic reaction. I am always getting stung when I grab fence gates where wasps have their nests. A month ago my arm was swollen for a week after I did not see a wasp nest on a fence.
Like the yellowjacket, paper wasps overwinter as fertilized queens hiding in cracks, crevices or under tree bark. In the spring the queen builds a small comb, lays a single egg in each cell then nurtures the larvae that hatch through several stages (instars) by feeding them bits of insects. Only when the larvae pupate is the cell opening covered. The adult wasps that emerge then take over expanding and caring for the nest while the queen continues to lay more eggs. In the fall the queen stops laying eggs, some female offspring mate and fly off to overwinter and the colony dies.
There is discussion about whether paper wasps, in general, are beneficial. Paper wasps feed their young insects that damage trees and crops as well as houseflies, blowflies and other pests. Since they are not aggressive, the balance usually falls toward beneficial. Whether the introduced European paper wasp is displacing native species is also an area of research.
These European paper wasps were photographed under the eaves of our bunkhouse and machine shed (Modoc County CA).