I JUST READ A BOOK that filled me with wonder and awe. Now, would it startle you to hear that it was a book about wasps? Don’t cringe and turn away; listen as I talk to entomologist Eric Eaton, author of the new book, “Wasps: The Astonishing Diversity of a Misunderstood Insect.”
That the world would be a much worse place without wasps, if it were a place at all, is what I came away thinking about after reading Eric’s new book. Eric is previously lead author on the “Insects of North America” volume (affiliate link) in the popular “Kaufman Field Guide” series. We talked about fear of wasps, yes, but also about how much they contribute to the environment–in pest control, pollination services, and figs, among other things (yes, tiny wasps make figs happen).
Plus: Enter to win the new book by commenting at the bottom of the page.
Read along as you listen to the May 10, 2021 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).
all about wasps, with eric eaton
Margaret Roach: Welcome to the program, Eric, or maybe I should say Bug Eric, because I think that’s what your blog is called. How are you?
Eric Eaton: I’m good. Thank you for the invitation.
Margaret: Yes. It’s a wonderful book. It’s beautiful and incredibly interesting. I thought I’d be afraid. And speaking of that, I learned a new word, the word for the fear of wasps. Maybe you want to pronounce it for me [laughter].
Eric: Oh gosh, it’s Latin, I think, it’s spheksophobia, I believe or spheksophobia … depending on your preference.
Margaret: Yeah. A subcategory, you say, of entomophobia, a fear of insects, which I don’t understand but a lot of people have that.
Eric: Yeah, I think we’re influenced by so many outside forces that it’s easy to become entomophobic, even if you don’t start out that way.
Margaret: Yeah. So can we define what you as an entomologist think that a wasp is, because I don’t think you just mean the guys in the paper nests on my back porch eaves, or hanging in the crabapple branches in the backyard that I come upon and go, oooh. I don’t think that’s all that a wasp is. So can you tell me your version of who’s a wasp, what’s a wasp?
Eric: Right. Exactly. Our cultural definition of wasps is what you just shared, which is the social wasps that we tend to associate with aggressiveness, because they’re defending a nest full of their vulnerable siblings in an egg, larva or pupal stage that can’t defend themselves. So their adult siblings do that for them.
But the scientific definition of wasps pretty much encompasses… It’s trending, actually, towards encompassing the entire order Hymenoptera, which includes wasps, bees and ants. And so all of those are traditionally known as social insects, but the overwhelming majority of wasps and bees are solitary, meaning that each individual female creates her own nest or in some cases there’s no nest involved at all. The wasp will simply lay an egg in a host, and then go on to do that repeatedly. [Below, a social tropical paper wasp nest in South Texas.]
Margaret: You said bees and wasps, I don’t know if you said hornets or yellowjackets, that’s another sort of word that we laypeople use. Sawflies, even, kind of look like wasps, but are they wasps, or what about the word hornet and yellowjacket and sawfly?
Eric: Yeah. You’re on point with all of those. All of those are considered wasps.
Margaret: To you as the expert [laughter].
Eric: Yeah. No, to science and that’s an agreed-upon definition. They’re just simply subcategories of wasps. Sawflies do not sting. They’re considered the most ancient in the lineage of wasps and their larvae are actually very caterpillar-like in most cases, and they’re feeding on foliage rather than on an insect host or a spider host or something like that, that many of the wasps we think of do. So hornets and yellowjackets are both in the family Vespidae, which includes those social species. And then it also includes solitary species known as pollen wasps, mason wasps, and potter wasps. [A mason wasp, below.]
Margaret: Sawflies, I think I read in the book, go back the sort of the oldest of the ancestors 235 million years maybe or something. I mean their long history on the earth.
Eric: Well, the evolution of wasps is still hotly debated. I mean, especially when you get up to the point where they diverge into social insects. And so the way we arrive at our conclusions is based on ever-increasing technological tools, and especially in the realm of molecular DNA analysis of existing wasps and seeing, well, O.K., what genes do they have in common with other extant wasps?
And the fossil record actually is, doesn’t form somewhat, but not probably as illuminating as you might expect. It’s more of tracing these ancestries back through analysis of living wasps.
Margaret: Right. So you say in the book—I love this—you say: “Periodic personal experiences with wasps may be painful, but our civilization would not be advancing without these insects and natural ecosystems would collapse where it not for the diversity of wasps species we see today.”
So can you tell us briefly about sort of some of these waspy contributions that they make?
Eric: Yeah. Like bees and many other insects, wasps can be pollinators. In the case of some flowers, they’re the only pollinator and we call them oligolectic. That may be a word that’s already familiar to your listeners, meaning that they’re obligatory pollinators of a very specific flower.
And there’s some wasps and flowers that have convergent evolution to the point where the flower actually mimics the female wasp. And so it’s the male wasp that is responsible for pollinating the flower. And this is true of several orchid species, actually, in Europe and in Australia in particular.
But if you like figs, you can thank wasps for that [laughter]. They’re pollinated exclusively by extremely tiny wasps. That’s the other thing, most people think of wasps as a pretty substantial insect, but the overwhelming majority of wasps are under 5 millimeters in body length. And fig wasps are especially tiny. And so they enter the fig through a special opening and go inside and pollinate, and carry out their entire life cycle, in fact inside the fig.
So in that sense, here we have an entire crop that owes its existence to and continued existence, to having an evolutionary symbiosis with these little tiny wasps.
Pest control is the other big contribution that wasps make to us in terms of food production and protecting our gardens. They’re constantly hunting for other insects to use as hosts, either where the host is or they will transport the host to a nest. So that’s a major contribution, I would say probably, the wasps make to humanity is keeping pests at tolerable levels.
Margaret: You say in the book that, “there’s hardly any insect species in existence that doesn’t have at least one wasp enemy.” So that’s pretty amazing, that they figure into so many other lives on the planet, so to speak.
Eric: Definitely, there’s a diagram I created for this book that shows how one generic moth species can host dozens of different kinds of wasps at each stage in the lifecycle, from egg parasitoids, wasps so tiny they develop entirely within the egg of a host. In some cases, several wasps per one egg of the host. And other wasps will lay their egg in the egg, but their larvae will develop inside the caterpillar. There’s other wasps that wait till the caterpillar is all grown up, sting it and transport it to a nest.
And then in the case of yellowjackets or paper wasps, they grab the caterpillar, chew it up and take it back to the nest to feed their larvae. So there’s one host organism can have several different wasp parasitoids or predators acting on it.
Margaret: I love another phrase in the book. You say that, “Wasps weaponized their egg-laying organisms,” and that the sting—and you point out it’s not technically called a stinger as we lay people call it—but the sting is unquestionably the greatest evolutionary achievement of wasps. So tell us about that [laughter]?
Eric: Oh, well, I mean it initially, probably, advanced from the egg-laying organ, which is called an ovipositor. And by the way, you have probably seen fairly good-sized wasps trailing an appendage that looks like a giant spear or a whip or some other …
Margaret: Amazing. It’s amazing.
Eric: … really intimidating organ, right. Well, that’s not a sting, that’s the ovipositor. And so if you see a wasp trailing an organ of that length, it’s not something that’s going to sting you, oddly enough. It’s when they don’t have something obvious on the rear of their abdomen [laughter] that you should probably take heed of, because the sting is a retractable organ that’s by the time it’s deployed, you’re feeling the pain basically.
But initially, in the parasitoid wasps—and by the way, a parasitoid is defined as a parasite that inevitably kills the host at some point—so the parasitoid wasp probably at some point said: “O.K., look, trying to lay an egg on a thrashing caterpillar is just not going to work. So let me paralyze it temporarily so I could do my business of laying an egg.” And so that’s probably how the sting came to be.
Margaret: I see.
Eric: And then it had an associated venom gland with it. And then as wasps continued their evolution, it evolved for social species into a defensive weapon. Some wasps, by the way, can even spray their venom out of their sting.
Eric: So, yeah. That’s probably how it happened.
Margaret: Cool, yeah.
Eric: But again, when it comes to the evolution of wasps, there’s a lot of gaps still to be filled in.
Margaret: Yeah. Do only females sting?
Eric: That’s correct.
Margaret: O.K. And all wasp species are capable of stinging, or some don’t?
Eric: That’s a very good question. Our definition of venom itself is changing.
Eric: I mean when I was growing up, things that were venomous were snakes, spiders, wasps, bees. But now we’re learning that venom is pretty much any kind of substance that is introduced to a host and affects the host in some fashion. And so now when you look at the relatives of sawflies, there are these insets called horntail wood wasps. And we have known for some time that they introduce… The female when she lays her eggs, introduces a fungus that helps predigest cellulose in the wood, so that her larva can feed more easily and gain nutrition from what they’re eating.
Now, it turns out that at least a few species also introduce a type of substance that weakens the tree, and allows the fungus itself to get a greater purchase on the host [laughter]. So we’re learning all these nuances all the time.
And so I’m not even sure quite how to answer that. Obviously, sawflies do not sting. We know that for sure, but some of the things that we have traditionally thought of as non-stinging parasitoids, like ichneumon wasps and braconids, and even some of the super-tiny micro hymenopterans, maybe they sting after all, but they’re so tiny that they wouldn’t even be able to penetrate your skin. So if you’re talking purely in, does it sting me? No, not at all wasps do.
Margaret: Right. You said ichneumon wasps, and the first time I ever learned about ovipositors, those crazy appendages, those thread-like things out the back end of a wasp, was from, well, I put two and two together. I had seen it outside in the garden, and then I read a book, I think by Bernd Heinrich, former University of Vermont professor and so forth. And his father had studied those in particular. And so I was like, “Oh, that’s what I saw.” You know what I mean? Because this was many years ago, I didn’t know.
You also mentioned what we would call the wasp waist, the sort of body structure, is part of the secret of the effectiveness of the sting, yes? The way the body is structured helps that sting operate, doesn’t it? [Above, a giant ichneumon wasp.]
Eric: Yeah. The abdomen articulates a little bit differently than in other insects. And so you’ve got, for example, a mud dauber [below], that’s got this long stalk between the perceived thorax, the middle body part where the legs and wings are attached. And then there’s this long stalk and then the perceived abdomen on the other end of it. And it can whip that in several directions to either defend itself, or usually, it’s used primarily to paralyze a spider, a victim, to take back to the nest. But the interesting thing is that stalk itself is part of the abdomen, and it’s attached to the rear of the thorax, but the part it’s attached to back there is also the first segment of the abdomen.
And so because of this strange anatomy, scientists, entomologists have developed different terms for it that don’t apply to other insects. And so you’ve got these body parts on wasps that other insects don’t have, and you have different names for the abdomen itself versus what looks like the abdomen.
And it can be very confusing, even for scientists, if they don’t agree ahead of time [laughter] on what they’re pointing at, so yeah. But yes, certainly the articulation of the abdomen allows the sting to operating in several different directions.
Margaret: Yeah. So you mentioned wasps, for instance, maybe paralyzing or subduing and eating a caterpillar, taking a caterpillar to use as food, or what else do wasps eat. And maybe even more important, does anybody eat wasps—like who’s their predator?
Eric: Oh, wow. Other wasps actually are among their chief enemies. There are some that attack adult wasps. There are parasitoids that attack other wasps inside their nest.
There are flies called robber flies that hunt wasps. There are satellite flies, as they’re known, that are very small flies that infiltrate the nest of solitary wasps and lay their… they actually deposit larvae rather than eggs into the nest. And so the fly larvae crawl into the nest and feed on the provisions that were intended for their host.
And there’s velvet ants, which are actually wingless wasps, that do the same thing. They infiltrate the nest of another solitary wasp.
So there’s vertebrates, birds, that certainly prey out of wasps. And because they have that sharp, horny bill, they’re pretty impervious to stings, but even so, some of them, like tanagers, will rip out the sting before they eat the insect.
Eric: There’s a picture …
Margaret: Never seen that going on here.
Eric: … in the book of a red-bloated caracara, which is a tropical raptor that just lands on a nest of social wasps and tears into it, and starts plucking out the larvae inside the nest. There’s something called a honey buzzard that’s also a raptor that does the same thing. It actually digs up a subterranean nest of yellowjackets and feeds on the larvae.
So there’s bears and skunks, love to tear into wasp nests to get to those juicy grubs.
Margaret: I’m always fascinated by insects that look like other insects. And if I were going to anthropomorphize and lay that on them, I’d say they’re very smart—the ones that decided to look like wasps. And of course, they didn’t decide, and it’s not necessarily about smart in the way that we think about smart, but the evolution of some other insects to have mimicked the appearance of a wasp to protect themselves.
Maybe we should talk about a few of those because, boy, there’s a lot of them out there when one is trying to figure out who’s a bee, who’s a wasp, who’s this, who’s that? There’s also these mimics, yes, these lookalikes? [Above, a wasp lookalike, a thick-headed fly.]
Eric: Oh, yeah. Yeah. Everything from beetles, to moths, to flies, true bugs, and katydids in the tropics that are… And they’re not even convincing just in appearance, but it’s behavior that they do that reinforces that. And I mean there’s katydids in the tropics that looked like these giant tarantula hawk wasps, and apparently, they move in such a fashion that even seasoned entomologists are going, “O.K., I think that really is a wasp.”
Eric: And there’s flies here in North America that they don’t have the same anatomy quite right as a wasp, and so they compensate for it. For example, they have very short antennae, and so they’ll compensate for that by waving their front legs to imitate the longer antennae of wasps. They’ll fly in a manner that’s very similar to a yellowjacket, for example.
Generally, if you see something hovering, it is not going to be a wasp. Flies are much better at hovering than wasps, and in fact, even most bees. So that’s one thing you can watch for, but probably, I’m going to just say probably half of the insects that the average person assumes are wasps, are not. The flies are often, the flower flies in particular, are often more abundant than wasps.
Margaret: Yeah. I want to just say, sort of as gardeners, how should we embrace wasps, so to speak, and make them welcome. And I mean, the ones on the other extreme that aren’t good roommates or wouldn’t be good roommates, I don’t know, I’m always inclined to dispatch a nest I see being built right by the porch or something. But in the outer reaches, it’s like that’s their world and they’re welcome to it.
But is there anything, I mean is it just a diversity of plants to take resources from that we should be planting, or is there anything that makes a wasp especially happy? I don’t even know if they use water in the same, use large resources of water, or they just take that from plants or what? [Above, a Northern paper wasp nest.]
Eric: They certainly drink, especially the ones that make paper nests or mud nests—they are often termed water carriers. And so they take water to a source of soil, or of wood fibers, and then turn them into nesting material.
My overriding philosophy is that: Don’t play favorites. The goal of your garden should be biodiversity in general.
Eric: If you’ve got all the players, things are going to take care of themselves. And so people, for example, who grow milkweed specifically for monarchs and then can’t tolerate any other insect on the milkweeds [laughter] really peeve me because…
Margaret: No, I think you’re right. Yeah.
Eric: So yeah, and be weed-tolerant, unless it’s a noxious weed that is listed for your state, maybe let it go and see if it doesn’t draw some pollinators. It could be a native wildflower. Product is really rarely something that is going to solve a problem. The major problems in our society at large and in gardens to, are your mindset, your attitude, so that’s really kind of the crux of it.
And remember that we manufacture more pests than exist in nature. A yellowjacket can’t tell the difference between your barbecue and the leftovers of a coyote kill, for example. It’s the same thing to them [laughter].
Margaret: Very well… that is a very good point, yes.
Eric: Yeah. And our architecture, for crying out loud. Our houses have overhangs, which mimic cliff faces and rock ledges that paper wasps and mud daubers and things naturally nest under. So of course, they’re going to look at our house as another cliff face, and behave accordingly.
Margaret: Exactly [laughter].
Eric: If you notice a nest and it’s already got several wasps on it, it’s probably not going to be a problem. If it took you this long to notice it, the wasps clearly… You and the wasp are not noticing each other or bothered by each other. So we had a bush in our yard once that had a hornet nest, but we didn’t know it until all the leaves fell off [laughter].
Margaret: Exactly. Surprise.
Margaret: Yeah. Well, as I said at the beginning, I was at first a little cringing and then I opened the book up and I started to read and I started to learn. And it’s great, “Wasps: The Astonishing Diversity of a Misunderstood Insect.” Eric Eaton, thank you so much for making time today.
Eric: Oh, my pleasure. Thank you.
(All photos from Eric Eaton’s Flickr stream. Used with permission.)
enter to win a copy of ‘wasps’ by eric eaton
I’LL BUY A COPY of “Wasps: The Astonishing Diversity of a Misunderstood Insect” (affiliate link) for one lucky reader. All you have to do to enter is answer this question in the comments box farther down the page:
How’s your case of spheksophobia going–or do you have more generalized entomophobia? Any insects that freak you out over there?
No answer, or feeling shy? Just say something like “count me in,” and I will, but a reply is even better. I’ll pick a random winner when entries close at midnight Tuesday, May 18, 2021. Good luck to all.
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the May 10, 2021 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).