Those wasps buzzing around your backyard or neighborhood park? They may be able to recognize each other’s faces. It’s a self-serving adaptation, likely evolved to help them know who ranks where in the pecking order of tough wasps.
The northern paper wasp (Polistes fuscatus), a species that ranges widely in North America, could be the only wasp with this ability – though it’s a little hard to say given the nearly 300 species of paper wasps in the world.
It’s also possible there are wasps keeping unwanted yellowjacket populations in check or devouring caterpillars that would otherwise be killing your backyard trees.
That’s the thing about this category of insects we call wasps, which broadly includes hundreds of species of paper wasps and dozens of species of yellowjackets and hornets. They are often maligned, hated for their occasional tendency to sting nearby humans and raid late summer picnics.
But they also serve not only an important ecological role, but are providing researchers with a fascinating ability to watch and track evolution in almost real time, says Sara Miller, a post-doctoral fellow in the Sheehan Lab at Cornell University, who published a 2020 study on northern paper wasp facial recognition.
“Because this is such a new trait, and we know it evolved recently, it gives us a really interesting insight into how complex cognitive traits might evolve,” says Miller.
What is a Wasp?
Before launching into how exactly some wasps know each other by face, here’s a brief explainer of all those yellow and black (and sometimes white and black) flying creatures with stingers that are, more often than not, confused for one another.
First, most of what you think of when you think of “wasps” are in an order called Hymenoptera that also includes ants, bees and sawflies. Break it down further to the family Vespidae, you’ll find yellowjackets, hornets, paper wasps and potter, mason and pollen wasps. Plenty of people call Vesbidae simply “wasps,” which Miller says is just fine.
What’s the difference between yellowjackets, hornets and wasps? Plenty, even if it doesn’t seem like it at first.
Wasps include everything from the ominous Asian giant hornet (often called the “murder hornet”), an invasive wasp known for a sting that feels like “being stabbed with a hot metal pin,” to the cicada killer wasp that, despite its ominous-sounding name, is no danger at all to humans.
The first way to differentiate species is by looking at nests. Paper wasps have open nests with visible cells. They also tend to be smaller with fewer individuals living inside. Even a big nest may only house 50 or 100 individuals.
Yellowjacket nests come in two varieties – some are built hanging off of trees or under building eves and are likely the ones you think about as enclosed, spherical nests. Others are deep underground. And yes, even the underground ones build actual nests in rodent holes, with intricate cells of paper crafted in total darkness, says Scott Schell, a research scientist at the University of Wyoming. Their nests can house thousands of yellowjackets.
European hornets tend to build nests in hollowed portions of trees or areas like attics.
Wasps, yellowjackets and hornets also vary widely in size and markings.
Know Your Neighbor
Show a person a photo of a house, then change about 10 percent of the house – sizes of windows, a few colors. The person may not really notice. Show them a picture of a human’s face, however, with about 10 percent changed, and they will notice.
As it turns out, humans aren’t the only ones keyed into the faces of those around them, and for good reason.
Northern paper wasps can have multiple queens in a colony, but there is a clear hierarchy among which queen is able to reproduce the most, then second, then third and so on. It’s the ability to cooperate in nests with multiple queens that has allowed northern paper wasps to not only persist but continue expanding their territory north as the climate changes and warms, says Miller.
Who is in charge, and who is next up, is quickly established by fighting. And it behooves not only individuals, but also the greater colony, if queens remember who is tougher.
“If they can recognize the other individuals they’re cooperating with, they can use it as shorthand,” Miller says. “They know if individual A fought with individual B, they don’t have to fight again. They already went through it.”
Other species of wasps have what researchers have called karate belt recognition. The European paper wasp and the Guinea paper wasp have patterns on their faces that shows how good a fighter they are, similar to the color of a karate belt.
“They use the facial markings to recognize the quality of other females which can be a shorthand that reduces aggressive interactions because they know their quality relative to other females without having to fight.”
Most interesting for researchers like Miller, is that those traits evolved independently from other wasps, which means specialized markings must be an important and advantageous adaptation.
Picnics, Caterpillars and Stings
Does this mean the wasps trying to crawl in your soda can or steal a bit of hamburger from your barbecue can recognize each other by their faces? Probably not. Those are likely yellowjackets, Schell says, and will only become more visible until temperatures drop.
Ground-dwelling yellowjackets often scavenge protein and sugars, and they tend to be the ones we see raiding picnics or, on occasion, stinging an unsuspecting person. Since queens begin nests in the spring and quickly build members over the course of the summer, nests are biggest as fall nears. Wasps will also be most fervently looking for food as summer wanes, to feed larvae and be sure more queens will be reared in time to hibernate for winter.
Yellowjackets landing on food or stinging arms are not ideal, Schell says, but pause before you take out your wrath on the nearest nest of tree-dwelling yellowjackets or the paper wasp nest tucked away from people.
Many species of yellowjackets, hornets and wasps aren’t actually much of a danger to humans, and many also help people out by eating insect pests like caterpillars and beetle larvae. Their larvae also provide food for any number of creatures brave enough to dig up or tear down nests.
“If you’re having problems with yellowjackets in your yard, observe for a while where the point of origin is,” Schell says. “Treating a nest in a tree is probably doing more harm than good.” And maybe even leaving more room for ground-nesting wasps, or invasive species like European paper wasps, to move in.