#4 :: Inside the nest
Intro music: "Wasps ain't nothing to mess with " by Cichlid Joe.
Jake Hello. You are listening to InsectaPod Cast, a product of the Michigan State University Dept. of Entomology. It's home on the web: www.insectapodcast.com. This is episode 4, Inside the nest. Today we look at a group of social insects many of us have become very wary of: paper wasps. Many of us are familiar with these yellow and black wasps that tend to become aggressive late in the summer and unwelcome guests at picnics. We'll look into the interactions we don't often see by focusing on one species of paper wasp. We examine how they enforce “rules” and “laws” without police and courts- basically, what happens when one of them cheats. We also get into how they form cliques and the benefits that female wasps get from staying in those cliques. I'm Jake McCarthy, the next voice you'll hear is Anna Fiedler, and this is InsectaPod Cast.
Anna We spoke with Dr. Elizabeth Tibbetts, Assistant Professor in the Ecology and Evolutionary Biology program at the University of Michigan, about how one species of paper wasp is similar to the honeybee, another social insect that typically gets more positive press. In honeybee colonies, the queen is the only bee who gets to lay eggs, while the remainder of the female bees are workers who do all of the hive maintenance and care of young. In paper wasps, however, any of the wasps have the potential to become a queen. Things get especially sticky when there are multiple queens in one nest, each vying for the right to pass on her genes by laying eggs. This is the case in one species that is invasive in the US. Although native to Europe, the species named Polistes dominulus has become more common in the Midwest in recent years. These brown and yellow wasps may be found nesting in house eaves or barbecue grills, and while they’re in places we’d rather not have them, some very interesting things go on in those nests. Elizabeth describes the fights that these wasps have to determine who gets to be “queen of the hill”.
Anna How do they determine which queen is the dominant queen?
Elizabeth So they determine dominance status by having intense battles where they grapple w/ each other, so they’ll stand up on their hind legs and it kind of looks like they’re boxing, and then sometimes they roll around and try to sting each other to death, and the winner is the dominant. But after dominance is established, they become very non-aggressive towards each other, so they don’t keep fighting for their whole life. It’s established, and then the winner stays the winner.
Anna These battles take a lot of energy and can even be life-threatening. Elizabeth’s research involves recording what happens when wasps square off with each other, and she’s seen one wasp chew an opponent’s wings off, and another get stung to death. These displays of dominance aren’t over quickly. The typical fight lasts for several hours, with longer bouts taking days to settle. With all the risks that go into these fights, it’s no wonder that once they’re over the wasps go back to coexisting peacefully. Establishment of who is dominant, which wasp gets to lay the most eggs and do the least work, is determined in part by patterning on their faces. In general, wasps with more spots on their face are more dominant, and the least dominant group of workers have no spots on their faces. 10-15 queens and 1-200 workers coexist in this colony, and they minimize the number of fights they get into by sizing each other up beforehand.
Elizabeth Wasps use facial patterns to choose their opponents, and they avoid opponents who signal that they’re strong. So the other side of this is the question of what happens if wasps cheat during a behavioral interaction. So, there’s big questions in communication about what keeps signals honest. If you think about it, animals are communicating with each other all of the time, and they don’t have the same kind of rules and laws we do to keep them honest. So why aren’t they cheating? Why aren’t they lying all of the time? Why would a wasp ever signal that she’s wimpy? And one possibility is (9:12) if she signals that she’s strong and she’s actually wimpy, she suffers some kind of cost. So that it’s a problem if you cheat. So I tested this idea by taking two wasps and using paint to manipulate the facial patterns in one of the wasps, so I took a wasp and made her signal that she was strong. Then I put her in a fight, and then observed what happened. And I saw that what happened is, she did not rise in dominance rank, she just got beaten up. So it looks like her opponent could tell that she was cheating, and she was punished by that opponent.
Anna This finding means that wasps are basically policing each other with a kind of corporal punishment enforced by a dominant when a subordinate gets out of line. In fact, while wasps fight, they appear to be assessing each other’s strength, and when a weak wasp signals that it’s strong with painted-on facial patterns, it will be treated with much more aggression than if it were signaling honestly that it was a subordinate. What’s even more interesting is that wimpy wasps are not necessarily physically smaller, indicating that wasps are using other factors to size each other up.
Elizabeth The wimpy wasps are smaller than the stronger wasps on average, but there are other aspects of strength that aren’t just size. For example, if you take two nests, and you give one nest access to lots and lots of food, and you give the other nest access to smaller amounts of food, the nest with lots of food will produce lots of wasps with very spotty faces who are signaling that they are very strong, and the nest with less food will produce lots of wimps.
Anna Scientists are not yet sure what the other factors wasps use to determine who’s the boss, but people do know that in colonies with more than one queen, the dominant queen guards areas of the nest where eggs are laid. The trick is that the queen must do so fairly- according to the other queens’ rankings- or those queens may decide to leave the nest and start their own colony. If a subordinate queen is cheated out of egg-laying space, she tests the dominant queen, becoming aggressive toward her, and in turn, the dominant queen actually becomes “kind” towards the usually submissive lower ranking queen.
Elizabeth When the dominant is being kind to the subordinate, it just means that she’s less aggressive. There’s usually like a basal level of aggression in a wasp colony that’s like, I think, 2 and a half aggressive acts a minute, so they’re relatively aggressive all of the time. So the dominant just kind of sits still and lets the subordinate do what she wants. Usually the dominant kind of polices where on the colony a subordinate can go and she’ll become aggressive with the subordinate if the subordinate isn’t doing things the way the dominant would like it.
Anna The nests themselves are actually much, much smaller than the typical basketball-sized enclosed paper wasp nest we take note of in trees. Nests this species of paper wasp create are open, rather than enclosed, which makes them easier for scientists to study. Paper wasps construct their nests in an ingenious way- and they need to go to all of this trouble each year, as only the queens survive the winter, and they locate a new spot for a home each spring.
Anna Let’s talk about what the nest actually looks like.
Elizabeth So they’re called paper wasps and their nest is made out of paper. Wasps go and – you can see them gnawing on wood sometimes, and they create this wood pulp that they then use to shape into their nest. Their nest just looks like an open honeycomb. There’s no envelope around it, and the species that I’m talking about. There are other species with much larger colonies and you’ll see them with globe nests with a paper outer covering, but I don’t study those. They’re harder to study as you can imagine, because you can’t see what’s going on inside the colony.
Anna Typically, nests that paper wasps create are gray and brown lumps of honeycomb-shaped cells. When we ventured into Elizabeth’s laboratory, that’s what I expected to see. The reality was a surprise, though, as the nests weren’t the size I was expecting. More surprisingly, because the nests are the color of whatever paper the wasps chew up to make them, they weren’t the dirty gray I expected either.
Anna I see a series of boxes that have either plexiglass or saran-wrapped fronts, and there are wasps in each of the boxes and up in the left-hand corner there’s a nest that’s attached in most of them- in most of them. Most of the time they’re silver dollar sized. Not actually as large as I would have anticipated. Do they actually use the box itself for nesting material?
Elizabeth Yes. They do.
Anna That’s pretty sweet. You have an orange nest here. Do you guys play around with that?
Elizabeth Yes. I have a friend who actually made rainbow nests, but I never have been that involved.
Anna How long does it take to make a rainbow nest?
Elizabeth You’ve gotta be vigilant about switching out the paper, it’s more what it is.
Anna So, give some nestless wasps a pink piece of paper, and they’ll start building a pink home. Switch the pink for green at the halfway point, and the finished nest will be two distinct colors. These are the sorts of things entomologists find amusing even while conducting serious research about insect behavior. Then, while we were admiring the vibrant colors of Elizabeth’s wasps’ nests, a research assistant was able to bring the conversation into the real world, and offered a tip on where we could check out a paper wasp nest in the wild, right across the street.
Research Assistant I don’t know what you guys are doing but if you want to see a gigantic nest, it’s across the street outside of the Michigan Book and Supply. If you look up into the lights near these big awnings and its in the light closest to here there’s a nest that’s, like, this big.
Anna And it’s the same species?
Research Assistant Dominulus, yeah.
Anna After leaving the lab we went across the street and tracked down the nest, a small gray one in a lamp can hanging off a bookstore. There were wasps active in the nest, and, just a few feet away, people active on the sidewalk— walking to work and class, unaware of the social microcosm in the street lamp right above them. Part of what’s interesting about Elizabeth’s research into the social lives of paper wasps is the fact that these complex interactions are going on in a group of insects that are often considered simply a nuisance. Pesky as paper wasps may be, though, a whole lot more than meets the eye goes on in their nests. The similarity here between insects and humans is that we both have established social hierarchies, based on rules. The difference I’d like to think exists is this: the options humans have are more complex and we can quickly adapt to the situations we find ourselves in. But underneath all that complexity, wasps and humans are still following some of the same basic rules of communication. Cheating doesn’t pay and cooperation is possible, even if it’s in a silver dollar-sized wasp nest.
Jake Thank you for listening to InsectaPod Cast episode 4, Inside the nest. InsectaPod Cast is a product of the Michigan State University Dept. of Entomology and is funded in part by the Ray and Bernice Hutson Memorial Entomology Endowment. Our home on the web is www.insectapodcast.com, if you go there now you can see some picture of that wasp nest we talked about, the one in the lamp by the Michigan Book and Supply. Otherwise, I'm Jake McCarthy, my partner is Anna Fiedler, and thanks for listening.
