The European Paper Wasp

A new arrival to the US, the European paper wasp has been a very effective colonizer.

This column appeared in The Recorder on July 31.

Last week I took a closer look at the wild parsnip (Pastinaca sativa). Specifically, I tried to highlight the amazing diversity of insects that can be found on this plant. I focused in on a mutualistic symbiotic relationship between ants and aphids. I also shared a photo of a European paper wasp (Polistes dominulus).

The wasp was something of a surprise for me. It had bold, distinctive yellow and black markings, but it proved quite difficult for me to identify. None of my field guides had anything that looked quite like it so I eventually went to the internet, typed “yellow and black wasp” into a search engine, and then started scanning the myriad photos that popped up. Eventually I managed to come up with a good identification. I then scanned my field guides and found that none had a reference to the wasp. Only one of my reference books had it listed and that one was published in 2006.

It turns out that the European paper wasp was not present in the US until 1981. At that time I was 13 years old and just starting to think about going into the ninth grade. By 1995, when I defended my Master’s thesis at U-Mass, Amherst, the wasp was spreading across the US quickly. It turns out that this native of the Mediterranean is much better suited for survival than some of the US species.

Most North American paper wasps are predatory insects that hunt and kill caterpillars. These prey items are then brought back to the nest where they are chewed up and fed to larval wasps. The nest may be rather large, but it typically consists of a single circular nest that is made up of individual cells, where the larvae grow. The nest is made of chewed up wood that has the characteristics of a thick paper. Thus, these are known as “paper wasps.”

European paper wasps are also predators, but they will prey on a much wider variety of insects than their North American counterparts. Instead of just focusing on caterpillars, the European paper wasp will go after flies, beetles, and other insects that they will then feed to their young. This makes them ideal colonizers because they can outcompete native species by finding more food and reproducing more quickly.

I once found a European paper wasp nest in a flowerpot that was made of compressed peat moss. The pot had been sitting upside down on my deck and when I flipped it over I discovered a beautiful little nest that was perfectly centered on the bottom of the pot. The adults had been entering and exiting the pot through drain holes and the nest was perfectly sheltered from any rain.

The nest contained larval wasps in several stages. Some were so fat that they completely filled their cells so that only their heads were visible. Some of the cells had been covered over with a hemispherical dome while the larvae pupated into adults. One cell even appeared to have an egg laid on the side.

Mind you, I didn’t notice all of this while actually taking the picture. The wasps weren’t exactly happy that I had found their nest, but they didn’t sting me either. Had I stumbled upon a yellow jacket (Vespula maculifrons) nest I might not have gotten out of the situation unscathed. Yellow jackets are also black and yellow wasps, but their markings are different and they are much more aggressive than other species of paper wasps.

Next week I celebrate another Speaking of Nature milestone, so I hope you are able to join me. In the meantime, stay safe, stay dry and keep your eyes open for something interesting out in the natural world. I have a feeling that August is going to be a very interesting month.