Speakers: Dr. Jason Schmidt, Associate Professor, University of Georgia (Tifton campus); Dr. Scott Clem, Assistant Professor of Insect Ecology, Illinois State University; Gabrielle LaTora, Agriculture and Natural Resources Agent, UGA Extension, Fulton County
Moderator / Host: Becky Griffin, UGA Extension (co-host: Rich Braman)
Duration: 1:20:45
Series: Great Southeast Pollinator Course
Webinar Date: July 21, 2026
Opening and Introductions
Becky Griffin: It is an exciting week here y’all. We’re going to talk about wasp and flies. And I don’t know who’s been more excited about that other than me because these are amazing insects. And I think y’all need to stay tuned closely today. You’re going to learn some really cool facts. And to get us started, I want to introduce Dr. Jason Schmidt. He is an associate professor at UGA and he’s on the Tifton campus. He focuses on arthropod ecology and trophic interaction. Basically, who’s eating what in your garden and why does it matter? His work gives us a deeper understanding of how wasps and other predatory insects fit into the bigger ecological picture. So, Jason, my friend, I am turning it over to you. Let me share my screen.
Jason Schmidt: Okay, I think I should be good now.
Scott Clem: Yeah, you’re looking good.
Jason Schmidt: All right, well, thank you again for having me. I’ll just introduce a little bit. Today we’re going to focus on flies and wasps. I’m going to get us started with some general background, because that’s what my lab is really focused on. And after that, Scott Clem, who’s assistant professor at Illinois State University, will talk specifically about flies. He’s an awesome specialist, and look at that enthusiasm in his smile as well. And after that, Gabrielle LaTora will talk about wasps, and she’s a specialist there, and will show us a bunch of things in that area of wasps. And I will get us started in this area of just general background on biodiversity provisioning.
Sampling Food Webs at Tifton
Jason Schmidt: Because in my lab we focus specifically on looking at to untangle the structure of communities and food webs to resolve when they change, why, what can we do to mitigate those things. And to do that we use workflow that looks something like this. So any type of biomaterial from the field — in this case, I’m showing soil in that number one. We take soil samples, for instance. We do DNA extraction. We do PCR to amplify what’s in there. That is, different types of organisms that are in there. And then far over to the left in six, we resolve then what species are hanging out in that area, or what types of pollen are hanging out on different pollinators, or what species are eating other species.
And so this is the general framing of what we do in the lab. But some of the reasoning behind that and where we fit that in is that we work a lot with producers of different crops and on different types of land, doing habitat enhancement and augmentation to facilitate biodiversity provisioning.
Habitat Work with Solar, Blueberry, and Apple Growers
Jason Schmidt: And some of the examples look something like this. So we’re partnered with solar producers to bring in and create an area where we’re doing more than just solar. We’re bringing in pollinator habitat. We’re bringing in habitat that could be used as grazing, things of this nature, which could look like this some of the time.
We also partner with producers. So this is a project where we did some corridor enhancement where we added flowers both on the side and then up into the corridor between blueberry plants to bring in pollinators. And you can see in that center picture there, you can see my van in the distance and then my camera. They’re taking pictures of different things in there to bring species into the field of different pollinators to aid in pollination.
We also then play with plant materials. So we plant plant materials in different areas to see how they perform and, you know, what species are then hanging out on them. So this is an example. Madison Love is leading this project and this is the Mercier Orchards in North Georgia, which is a large apple orchard and also does agritourism there.
Why Insect Diversity Is Worth Counting
Jason Schmidt: And one of the reasons that motivates this side of biodiversity provisioning is that while we might think that America’s kind of breathtaking landscapes are kind of timeless, and we don’t need to do anything — it’s just going to continue to be like that — the story is probably different, in that we see species of a variety of different types witnessing some types of declines. I know that in most of our conversation on pollinators, we’re focused specifically on bees. But if you look at this poster produced by the Pollinator Partnership, they show a bunch of other pollinators depending on where you are, from both bats, birds, butterflies, bees. And today, why this lead in is for those flies and wasps.
But one of the reasons why I think the group here focuses on insects in particular is not only because they’re just awesome, but because insects are really integral in the functioning of the planet, I think we could say, in terms of agriculture, in terms of human productivity. They are parts of all kinds of the ways in which our systems function. And so I think that’s one of the reasons why we focus on them, aside from our other love of insects.
And to emphasize this, a few years ago, a group produced this book, the Insect Atlas. And I’m not going to go through all these lessons. You can look this book up. I think it’s an awesome book on this. But I just wanted to emphasize two on this note on biodiversity. And that is that one is that about 90%, you know, estimates suggest around 90% of all animal species in the world are insects. They are one of the most abundant and numerous living things outside of bacteria and fungi and things of that nature. But of the large macro scale things that fly around and do stuff, insects are certainly some winners. And as you know, and part of our conversation here is that insects pollinate and many crops require this pollination. And it’s not just bees, although the conversation is often on bees.
So having all these insects and whatnot, why is it important, or aspects of the diversity important? And research that has brought some of these indicators together suggests that yes, when we increase or we have areas with higher amount of pollinator — so in this little graph at the bottom, this is a review of a whole bunch of different studies. As pollinator richness increases, generally we would get an increase in pollination. That is the success of transferring pollen and having pollination of a plant that could lead to either, you know, those species being there, wherever they’re native plants, or pollination, that is to provide a fruit or a vegetable that we eat.
And this is true also for this other category that you may have more or less information on, and that is these natural enemies. That is species out there, diversity of species that feed on certain pests. Pests, that is, it could be a plant that grows out of control, you know, and has to be controlled in an agricultural system or in a field or whatever. Or it could be another insect that grows also out of control and is not being controlled. So having more types of these natural enemies feeding on pests tends to lead to greater pest control.
Diversity You Can See: Color, Size, and Life Stage
Jason Schmidt: So diversity matters in a variety of ways. But when we talk about diversity, what really is that? And today, these two groups, flies and wasps, that they’re going to talk about, they’re going to show you some of that. But in general, I want to show you a few things. And I think one of them already comes to mind when we think of diversity. And this is one that’s easy to show. And that is diversity. Color and form is something in insects that is just spectacular.
If you look around this screen, what I’ve put together is a variety of different things. You probably recognize the spider in the center. Some of you like it or don’t like it. And then you have the spider up in the corner, which is a male jumping spider that uses that coloration for a mating display. And then you have color of wings and all these things. So color and form aesthetically are one that I think we all agree, if we’re interested in those sorts of things, that is a part of diversity that’s just awesome and why we like doing things in nature and studying stuff.
Size: Georgia’s Lady Beetles Down to Two Millimeters
Jason Schmidt: But on the functional side, one that I’ll illustrate with this little example here — you’ll have a beetle class I think next time. But in Georgia alone, there’s a range in size of the types of lady beetles out there. I know we often think in that left hand corner, this is our ladybird model. We say, oh, there’s a lady beetle. And that’s what we think of. And we also might think of this one below there, Harmonia, which is the multicolored ladybird beetle. This one, these are both very large.
But across the spectrum, if you go to the right, this is a size gradient of different sizes of these ladybird beetles that we would find just in Georgia alone. And around the world, there’s even more, ranging down even to only two millimeters long, and larvae there you wouldn’t even recognize as a lady beetle and that [VERIFY: "skimness" unclear], but this is a common predator that would feed on certain things. So size diversity is an important one, and I think you’ll see that in the flies and wasps as well.
Life Stages in Geocoris punctipes
Jason Schmidt: Another one is life stage diversity in insects is quite interesting. So this is a favored predator that a lot of folks like. This is Geocoris punctipes, and this shows over its lifetime, if you look at this little egg — this little egg is laid and you see that little tiny nymph here. And by the time it’s an adult, it’s many times larger than what it was as a little tiny one. The other thing that’s really different than you can see here is that the adult form has a lot of characteristics that that little tiny nymph doesn’t have. That is, the little tiny nymph can wander around very locally. Its ability to move around and eat on things and its function is quite limited because it’s so small and it has no wings.
Only until when it’s adult does it get those wings and can actually move around. So the things that these different life stages are doing are likely different. And at the adult, this is the only stage where they’re able to mate. Up until that point, they have no reproductive parts. So they molt, they grow, and then finally at this final stage, they get reproductive parts and they also get wings. So they can reproduce and they can also fly. So having a size diversity of these things out there is something important.
Mouthparts and What They Tell You
Jason Schmidt: Now getting closer here to things and conversations of today will be something you might not think of as easily, and that is insect mouth parts vary considerably, and so does the function then of what those insects are doing. So this is an example of a group I’m sure that Gabrielle will talk about today, and that’s Vespidae. And you can see in the upper panels, A, B, and C, these are all types of vespids that have kind of short mouth parts. You can see that they’re also, they have kind of teeth on them as well. So they’re very rigid and they’re short. And then if you look at the below panels, the D, E, and F, you can see that these are very long. It looks like you can see very long tongue. You can see other kind of things on there and extensions. So obviously the types of things that each of these different species are doing are likely different. So therefore their function in our systems is different. So having a variety of them means that we are probably doing different things, providing different functions in the systems.
A few more examples, because I think mouth parts are pretty awesome. Here’s a range of mouth parts from a variety of different insects. On the left hand side, this is a huge mixture of different things with one, a couple of interesting ones. If you look at the left lower hand panel, this is a type of part on a large bug that looks basically like a spear. And that’s basically what it is. It’s a spear and a straw. So this — the bug basically spears the prey item and drinks the body fluids from that victim, from the prey that it ate. Whereas other ones have very chewing parts. So if you look in the lower right-hand panel on the left-hand side, you can see ant mouth parts there, where you can see that they’re rigid, they have teeth, they’re chewing things up.
And that’s the same for the whole right-hand panel, which is to show the diversity of just one family of beetles. And these are the tiger beetles that are very colorful and whatever. But if you look, the types of structures on each of those different beetles is quite different. So they’re doing different things. They’re eating different things out there. And so having the diversity means you’re eating a lot of different things.
In the center, getting closer to these flies, is one that we don’t like. And there are, for every, you know, a thousand insects that we have no idea what those insects are even doing, there’s a few like this mosquito that we know what it’s doing, and we don’t like it. We don’t like to be bit by things, and mosquitoes are one that we don’t like. And you can see this one enjoying using its mouth parts to drink blood and become engorged with your blood, and this is something we don’t like. But again, with every one, there’s a thousand we don’t know what they’re doing, and a thousand that have very beautiful things going on. So anyway, insect mouthparts and other organism mouthparts are one of the features that is part of this diversity package that we’re going for.
Wings, Flight, and Micro Air Vehicles
Jason Schmidt: Now one more leading into our thing today, and the two groups that we’re talking about today are super flyers. This is not a fly. You probably recognize this one. It does have fly in the name, but this is a dragonfly. And a few of the characteristics can be carried over into the flies in that, if you look at this dragonfly, its head is basically all eyes. Which is interesting. If you take a moment to think about that, if your whole head on each half was just eyes, what the world would look like and how you would respond in that world. Very different to how we are able to respond. And they’re very fast at being able to respond, but they’re also moving fast in the environment.
So wing diversity, I’m just going to show a few until we lead into this next section. But one feature that’s really important, especially for identifying different insects, especially in the Hymenoptera and also in flies, would be the venation. So here’s a spectrum of different venations from a whole bunch of different taxa of insects, showing that the venation on wings, the shape of wings, the… varies.
The thing about wing size and structure has carried over into some interesting things in science as well. So here’s the two panels. The upper panel has a label that says animals, and then across there it says bee, butterfly, dragonfly, beetle. And yes, there’s a bird and a bat in there. And then the lower one is labeled MAVs, and this is micro air vehicles. So creating little miniaturized or semi-same size drones that modulate or emulate the types of structures that you would find on a bee, a butterfly, and a dragonfly. And these are different. The way that they’re able to fly is quite different because of that.
The one interesting one that you’re not going to be talking about with the bees — or sorry, with the wasps or the flies today — is the one you’ll talk about next time with Joe McHugh, and that is these beetles and how they’re able to hide their wings, which is pretty interesting. We won’t be talking about that today.
Take-Homes and the Pollinator Partnership Poster
Jason Schmidt: So a few take homes here on leading us in is that preserving biodiversity is important for the future and is recognized to require and requires active involvement. That is, now we’re at a time that enhancement is something that we’re doing, augmentation of habitat to provide spaces for things to live.
Biodiversity takes many forms. So hopefully I conveyed that today, that when we’re thinking about biodiversity, it’s more than just biological diversity. That is, biological diversity takes many forms. And today I shared a few of those and showed them, that is size, color and shape, mouth parts, wings, and the ability to fly, without talking very specifically about how different insects would fly based on the types of wing.
And with that lead in, our two next speakers in this area will be one on flies, which is Scott, and following that will be Gabrielle. And with that, I will end, Becky.
Becky Griffin: All right, Jason. Thank you. Thank you. One quick question. That poster that you showed with all the different, with the bat — is that something that other people can get?
Jason Schmidt: Yep. It’s freely. I can give you a link. There’s a freely available one. And in the background for me, I have a couple other ones that are freely available. You can — they even offer them to you in a pretty large scale. So you could print them as a poster or you could print them pretty small. Yep.
Becky Griffin: Is that pollinator.org?
Jason Schmidt: I think so, yes. I think they have them listed there. They just had a new one come out. I almost copied that one in. They had a new one come out, but they put one out, I think, like every year. And I emailed them once upon a time because I was like, I tried to print one of the one you could download. And I said, do you have a larger format? And they were happy to give me one. I said, you know, I’m not going to sell this or anything. I just want to put it in the lab. And they’re like, oh yeah, no problem. They sent me the full format. So.
Dr. Scott Clem: Why Flies Deserve a Second Look
Becky Griffin: Excellent. All right. Perfect. Well, thank you so much, Jason. That’s a great introduction. I loved all your pictures. So next up, we have Dr. Scott Clem. Dr. Clem is an assistant professor of insect ecology at Illinois State University. He is a former postdoc at UGA Department of Entomology. So he is buddies with all of us and we’re so happy to see his face today. His lab focuses on the ecology, behavior and biodiversity of beneficial insects with a particular emphasis on hoverflies. And any of you who’ve taken any of my programs know that I love hoverflies. And once that you figure out what they are, you find them everywhere. So basically, Scott is a fly fanatic, and he hopes today to inspire us all to love flies. And with that, Scott, I’m turning it over to you.
Scott Clem: Awesome. Thank you so much, Becky. Let’s see. I’m going to get this shared. Okay. Does that look good?
Becky Griffin: Sure does.
Scott Clem: All right, everybody. Yeah. Thank you so much for the introduction. I’m super excited to be here. And I hope that, you know, I can inspire you all to appreciate flies after this talk.
So I am a dipterist, which means I study flies. As such, one of the major topics in my lab is fly pollination. So flies are often brushed off as unimportant or uninteresting insects. But if you think this, I am here to say to prove you wrong. By the end of this talk, my goal is to have you walking away with newfound appreciation for flies, as well as their diversity and the important ecosystem services that they provide. I promise you won’t become a fly person like Jeff Goldblum in The Fly, but I hope to at least, you know, teach some of you to love them.
What Makes a Fly a Fly
Scott Clem: Okay, so first things first, what is a fly? There are several insects which are colloquially referred to as flies. If you think about like dragonflies, like Jason mentioned, or like butterflies or sawflies or mayflies, different things. These are all things that aren’t members of the order Diptera, but they have fly in the name.
But flies often look like other insects. And they can be kind of confusing to the untrained eye. What is a fly and what is not? So when in doubt, count the wings. Flies have two wings. There’s one pair of wings. So you see here that we have in the middle here, the flies clearly has two wings. Flies also have very large eyes compared to the rest of its body. So if you look closely, you’ll notice that flies tend to have very big eyes, whereas bees and wasps tend to have pretty small eyes. They also tend to — they don’t have a pollen collecting basket called a scopa. That’s what you see on several different bees. They have this massive scopa on their hind leg. And yeah, they also tend to have shorter antennae. So if you look at an insect and it has very short antennae and two wings, that would tell you that it is a fly. And so, yeah, just look closely at your insects and you can clearly, if you look closely, it’ll start to stand out to you the difference.
And this is what this looks like using some real pictures here. So on the left, I have a honey bee model, and on the right, I have a hover fly mimic. So the mimic clearly — well, here it’s actually hard to kind of tell, but it has two wings situated right here. Whereas the honey bee has four wings there. But you’ll also see that the hover fly has these larger eyes and shorter antennae. Whereas again, our honey bee does not have that. And then also there’s this big pollen collecting basket here on the honey bee. So these are kind of the major characteristics that differentiate flies from bees. And as you’ll see throughout this talk, there will be multiple cases of flies that resemble bees and wasps.
Myophily: Flowers That Court Flies
Scott Clem: Okay, so what are the basics of fly pollination? So the term fly pollination is referred to as myophily. In Greek, that is myia, meaning fly, and philos, meaning loving or affinity. So these are flowers that are pollinated by flies. They, for flies, most often visit flowers in the search of nectar and pollen. And in the process, they’ll pick up that pollen and it’ll get stuck on their many hairs or between their body segments or on their legs, different things like that. And then it’ll move that pollen to a new flower where it can achieve pollination.
So one thing that is different from flies to bees is that flies are non-central place foragers. This means that they have free living larvae and they don’t constantly have to return to a nest to provision those foragers, those larvae, with some sort of food or something like that. So they’re essentially flying around without, again, returning to a nest. It doesn’t have a nest, unlike most of your bees and social wasps.
When and Where Flies Forage
Scott Clem: Flies also are, they tend to be active during cooler times. So you often find them, if you’re looking at flowers, you often find them to be more active in the mornings or maybe late afternoon. Not in the heat of the day. They tend to avoid these really hot parts of the day. They also tend to forage in the shade a little bit more. And you also tend to find them more commonly during the spring and fall, where you actually get several species that actually will come out in greater abundance during those periods. But it’s highly variable. There’s lots of flies out there.
Generalized and Specialized Myophily
Scott Clem: And broadly speaking, when it comes to fly pollination, there are two categories. You have generalized myophily, and this involves plants that are not specifically adapted for fly pollination, but receive fly visits among a whole slew of other pollinators. This is our most common case that we see when you’re looking at any given flower and you see different flies visiting it. But a second category is specialized myophily. And this is where plants have evolved these specific floral traits that are clearly intended to attract flies. Often this comes in the form of scent, but there are also visual cues that pull it in.
So I’ll mention several examples here in a bit, but pictured in this right-hand, you know, this collage here are several examples of myophilous plants, most of which are specialized cases. So you get things like the corpse flower here, Rafflesia, that smells like rotten corpses and it pulls in pollinating flies. You also get some other species. This one’s a kettle trap flower. This one represented by G there. That’s one that actually traps the fly and then forces it to pollinate and then it will release it. Or it will force it to pick up the pollen and then it will release it. Jack in the pulpit is actually a species we have in the southeast that does a similar thing. But yeah, all sorts of examples, interesting examples of specialized cases of fly pollination.
What Fly Larvae Do for a Living
Scott Clem: So one thing that’s important when you’re understanding fly pollination is also understanding what the larvae are doing. So as I mentioned, flies have these free-living larvae, and they can occupy a wide range of ecological roles. They can be aquatic filter-feeding, like the rat-tailed maggot, pictured by A there in the top left. They can also be predators, which is B here. This is a predacious hoverfly larvae. They can also be wood feeding, which is C there. They can be necrophagous. That means they feed on dead and decaying animals or various things. E is a parasitic fly that — so the little tiny fly here — is actually a parasite of carpenter bees. So the bigger maggot here is a carpenter bee, and then that is our… it’s actually a bee fly that’s a parasite of carpenter bees. And then the final one example here I have is a herbivorous gall midge.
And so fly larvae are highly diverse. And they do a lot of different things. But my purpose of showing you this is just to show you not only their diversity, but also demonstrate that these life histories have important ramifications for pollination as well. So where adult flies found, what type of flowers are trying to draw them in, different things like that.
Five Groups of Flies
Scott Clem: So, true flies are one of the most diverse, if not the most diverse, groups of animal life on the planet. There are currently over 160,000 described species of flies, and at least three to five times more than that that have not yet been described. So of that, there are approximately 150 families of flies, and at least 70 are anthophilous, meaning that they visit flowers, and they can potentially contribute pollinating services. So, probably somewhere around 85,000 species are pollinators to some degree.
So here in this diagram, I’ve broken up, I’m showing you five different major groupings of the flies, which I will cover one by one here. And then I will take a deeper dive into the hover flies, which are the group that you might be most familiar with.
Nematocera: Midges, Mosquitoes, and Chocolate
Scott Clem: Okay, so I’m going to start with the Nematocera. So Nematocera are considered, they consist of more of our, you know, primitive flies with these long slender bodies and they have multi-segmented antennae. And this includes many of our familiar insects like mosquitoes and midges and march flies, or you might know them as love bugs, and then also crane flies. And these are among the most numerous flying insects in most terrestrial ecosystems. And as a result, they are extremely important. And they act as vital prey resources for numerous birds and mammals and spiders and other predators.
And because they are so numerous, they also can be important pollinators. So on a poor per visit basis, they are usually considered poor pollinators to flowers. But by simply being so numerous, they can actually play a significant role in pollination. And so there are generalized cases, but there’s also several specialized cases which you’re seeing here.
So one huge family, the gall midges — this is Cecidomyiidae is the family — have evolved these tight co-evolutionary relationships with plants. In some cases you get brood site mutualisms in which the plants allow larvae to form galls and feed on their tissues in return for adult pollination services. So you have these plants that actually are trying to accommodate the flies.
You also have interesting cases with mosquito pollinators. Believe it or not, mosquitoes can be pollinators. They are actually surprisingly prolific visitors to flowers. And they can, there’s a number of generalized and specialized cases. Male mosquitoes are actually very, almost exclusively dependent on nectar as a source of sustenance. And so it is even hypothesized that their elongate blood sucking mouth parts of mosquitoes, like Jason just showed you, actually it evolved originally as a way of sucking the nectar out of long tubular flowers, and then eventually over time transitioned into blood feeding.
Yeah, an example of a specialized mosquito or midge pollinated plant in the southeast is this pale green orchid here, which is actually a threatened species. It has these tiny little flowers that are dependent on nematoceran and other tiny fly pollination. And then another important case here is with cacao flowers. So cacao obviously produces chocolate. But cacao plants are primarily pollinated by midges. This means that the entire chocolate industry, worth about $120 billion, is entirely dependent on these two to three millimeter midges, these teeny tiny little midges. And so yeah, there’s many interesting cases of nematoceran pollination. Nematocerans also tend to pollinate at nighttime, so that can also be an important part that separates them from other groups.
Lower Brachycera: Long Tongues and Bee Flies
Scott Clem: Okay, so the next group is the lower Brachycera. So these represent many species that have these long proboscis that are built for extracting nectar. These include things like our, you know, bee flies, which you may be familiar with, as well as soldier flies, and even horse flies. That’s right. Horse flies can be pollinators when they’re not causing a nuisance.
And several of these groups are common in the southeast. And that picture on the right here, this is a tangle-veined fly. And I think this illustrates that long proboscis very well. Tangle-veined flies are actually found in South Africa, but they have these insanely long mouthparts, that are these proboscis that are three to four times the length of their body, that they reach down into those deep floral tubes.
Yeah, so yeah, lower Brachycera can also include some of our largest flies, such as the mydas fly that you’re seeing right here. This is this big black fly, and they’re actually out and about right now. They tend to come out in July, so take a look, see if you can find them. They are, they look like massive black hornets. But they can get up to an inch and a half long or so. So they’re these big, huge pollinating flies.
But perhaps the most well-known pollinating fly in this group is the bee fly. So these, what I like to call these flying fuzzballs — this is perfectly illustrated in this picture here of this bee fly that literally looks like a fuzzball. I think it even inspired a Pokemon that was created. And so there are several of these bee flies are what I think are arguably the nature’s cutest pollinator out there. And there’s several species that are found in the southeast, somewhere around 150 species. They tend to prefer sandy soils. And so especially as you get further south into South Georgia and Florida, you get all sorts of interesting things.
Another common bee fly that you find are the tiger bee flies. These you’ll find just flying around in your neighborhood. They are actually parasites of carpenter bees. So I showed you a picture of one earlier of the larvae. So there’s several different common bee flies and they can be important pollinators. Most bee flies are also parasites of either spiders or ground nesting spiders or ground nesting bees. So they actually sit there and they fling their little eggs into the burrows of ground nesting insects.
Calyptrates: Blow Flies, Pawpaws, and Stink Stations
Scott Clem: Okay, the next one is calyptrate flies. So this includes many of our famous or infamous flies like house flies and flesh flies and blow flies and all these others that tend to be unwanted visitors to your picnic. These actually can be really some of the most abundant pollinators in many systems, especially in highly degraded landscapes, because they actually have very fast growth rates, other populations do, and so they can actually succeed, or some species actually can succeed quite well in degraded landscapes.
And so many of these flies feed on dead and decaying things and many plant species have actually developed a means of attracting them for this reason. So I talked a little bit earlier about the corpse flower, the corpse lily here that smells like putrid, rotting animal or whatever. And it draws in all of these flies that are actually mistaking it as a place to lay their eggs. But they pick up that pollen and they carry it to the next corpse lily.
So, and this isn’t limited to tropical species either. We actually get lots of interesting cases of this in the eastern North America, such as pawpaws. Pawpaws actually have this really dark maroon colored flower, and they tend to smell. And so they draw in lots of flies and beetles and other things. And actually, pawpaw growers have developed, they attempt to draw in flies by incorporating what are called stink stations. And these are basically, you know, just big boxes of dead things that draw in flies into their orchards so that they can pollinate. Whether or not they actually work, I don’t know, but it’s an interesting way of achieving pollination in pawpaws.
Other cases, parasitic bristle flies are very — these are important for biological control. So that means they feed on, the larvae feed on various, you know, pest species insects like caterpillars or stink bugs or various other things. I’ve included a common species that we get that people often see visiting flowers. It has this kind of bright blue abdomen. They’re very hairy. They’re about the size of like a bumblebee, so they’re pretty big. And so, this particular species, you’re likely to see visiting your flowers on occasion. This one feeds on cutworms, fall webworms and corn earworms. So they’re actually really important.
So, yeah, so another very specialty case is with pitcher plants, actually. So pitcher plants, if you’ve ever been to a pitcher plant orchard — sorry, a pitcher plant bog — they have these interesting reddish flowers, and there’s a specific species of flesh fly that develops in the pitcher plants or in the tissues, and the adults actually provide pollination. So it has this intricate relationship with this particular pollinating fly here. So there’s lots of interesting cases.
Acalyptrates: The Taxonomic Trash Bin
Scott Clem: The final group before I get to hoverflies, these are the acalyptrates. So acalyptrates, if you’re curious, what defines an acalyptrate versus a calyptrate? So I talked before with a calyptrate, they have these big white — here I’ll go back, if you look, these, this right under the wing, there’s this big white structure, that is called a calypter, and that is what defines calyptrate flies. And so acalyptrate flies don’t have that.
And so this is a very large and diverse group of flies that are — that basically I call them a taxonomic trash bin because it includes so many different species that don’t really resemble one another and they’re not necessarily even closely related to each other. And so a common one that you’re likely to see at flowers is something like a thick-headed fly here. These are actually parasites of bees, things like bumblebees and some other species. They actually hang out on those flowers and they’ll catch the bee and then they’ll lay its egg on the bee and then larva develops inside the bee. So it’s this whole thing. But they’re actually pretty large flies and you’re likely to see them oftentimes. They are also likely to achieve pollination just like our — just alongside their hosts because they’re just hanging out on those flowers.
Most acalyptrates, however, are very tiny, somewhere between 1 and 5 millimeters. They have very short mouth parts. And so this often limits their pollination abilities in many cases. But there are many exceptions to that. So, for instance, there are some cases of where you get fruit fly orchids in the tropics that actually mimic the scent of like a fruity scent and it draws in fruit flies to pollinate them. And you also get parachute plants that actually mimic the pheromones of dead honeybees, which draws in these kleptoparasitic flies called freeloader flies that will visit that flower and pollinate it. So there’s really interesting cases of really specialized pollinating relationships here with this group.
Hoverflies: The Flying Eyeballs
Scott Clem: Okay, so I’ve saved the best for last. These are the hoverflies. So these are also known as flower flies, and the adults are almost exclusively pollinators. So the adults come in many different forms. You get very large species, almost the size of, you know, a yellow jacket or larger, and you get species that are like bumblebee mimics, and then you get species that are very teeny tiny, downwards to just a couple millimeters.
And, you — I like to call them flying eyeballs because when they hover, oftentimes all you see is their eyes and it’s just like a bunch of flying eyes, because again, flies have these very large eyes. And so you’re oftentimes seeing that. There are about 6,200 species worldwide and there’s somewhere around 250 species in the southeast. And so you’ll often just find them hovering around. Many are also migratory, which I’ll talk about in just a second.
Inside the Hoverflies
Scott Clem: There are four major subfamilies here, but two — four subfamilies, two major ones that you’re likely to see in your backyard.
Syrphinae: Garden-Variety Aphid Hunters
Scott Clem: The first subfamily is the subfamily Syrphinae. So these are the garden-variety syrphids, I like to call them. These are the ones that are very common. You might even recognize if you’ve looked at — I’ve done a lot of pellet pollinator observations — you’ve probably noticed something like, you know, Toxomerus marginatus down here in the bottom right, or Toxomerus geminatus. These are small, pretty small flies. Some people call them sweat bees because they actually come to your skin and feed on the salt on your skin. But you also get some other species like Eupeodes americanus, which is a really common one that is really abundant in the fall. And this one is several, you know, significantly larger than the tiny Toxomerus species.
And so one thing that makes this group distinct is that the larvae are predaceous. So the larvae feed on aphids and they’re important for biocontrol. And so here are some pictures of larvae and pupae of these hoverflies, of the syrphine hoverflies. They can range in color from brown to green, or even this one is a mimic of bird poop that you’ll find around the… And the larvae just kind of, they resemble little tiny slugs, and they’ll crawl around, grab onto those aphids, and just suck the juices out of them. And they are, they can eat, you know, several hundred aphids across their lifetime. So, so if you can imagine, you know, having a bunch of these out there can be really important for controlling aphid populations.
And it’s just an illustration of a larval hoverfly munching away on aphids. And so on an aphid here, see how it’s right here on the right, that’s actually its heart beating. But you can see that it’s got these little mouth parts that just kind of slice into the aphid and then suck those juices out.
Eristalinae: Born in Dead Wood and Tree Holes
Scott Clem: But not all of these hoverflies are biological control agents. Actually, a large amount of them are not. So about 65% of the species are found in the subfamily Eristalinae. And so this is, you know, there’s probably about 500 species of these in North America or so. These are more often found in forested habitats. I mean they’re extremely diverse, but often found there. They can be very — this is because the larvae are, they feed on dead and decaying things. Oftentimes they live in like dead wood or in, you know, tree holes, which is where, you know, you get like a hole in a tree that fills up with water. And so lots of larvae live in those situations and those types of habitats.
So these are the hover flies that are our best mimics. You get species like Spilomyia longicornis that is a very good mimic of yellow jackets. Eristalis tenax, again, this is the drone fly that mimics honeybee drones. This species up here in the top right, this is a bumblebee mimic. And so as you can tell, it’s a very good mimic.
And then the final one I wanted to mention was here is the Virginia giant hoverfly. And so this is one that you may have seen or even heard because they’re very loud when they fly. These things are about an inch long or so. They’re our largest hover fly. They’re yellow jacket mimics. They are called the news fly because they — the legend goes that they hover up in front of your face and they look like they’re inspecting you, but they also look like they’re delivering the news. So that’s why we call them news flies. I like that name. And so there’s like a whole history where, you know, poor Southerners that hung out on porches all day used to, you know, see these flies flying around and visiting them while they’re hanging out, drinking their tea or whatever. So, so anyway, I’m going to go.
Larvae of these flies, again, they have a wide range of types of habitats they live in. You get ones like this, the rat-tail maggot here, again, this is one in the bottom right, and these, again, live in, like, tree holes, whereas this other species, Xylota here, lives in, like, dead wood. Some of them are herbivorous. But yeah, there’s all sorts of various life histories that these insects have. And it kind of illustrates the importance of maintaining healthy forests. If you don’t just leave some dead wood around, you’re likely not going to get all of these interesting pollinating hoverflies because there’s nowhere for the larvae to live. So this is why we need good conservation strategies that don’t just take out all of the dead and decaying wood.
So the life cycle, basically the adult fly here is flying around. It finds some stagnant water somewhere, lays its eggs. It has this sort of circular pattern. Those eggs then hatch. The larva lives underwater and it has this long breathing siphon. That’s why they’re called rat-tailed maggots, because they have this long breathing siphon that allows it to breathe above the water there. Then it eventually crawls out and pupates and then we have an adult fly. And so again, this just illustrates what these flies are doing and how they’re just — yeah, what’s going on, what types of habitats they tend to require.
Hoverfly Migration and Georgia’s Species Count
Scott Clem: And another thing about hoverflies is that they actually, much like monarch butterflies, they exhibit seasonal migration. And actually this is what my research is on. And what you’re seeing here is a — this is actually a diagram of North America, and I used what are called stable isotopes to try and understand the migratory origins of flies. So green is actually the most likely area of origin. So what I found is that somewhere around August and September, a bunch of these flies fly thousands of miles or thousands of kilometers down south and where they then occupy the southeast for a little while. And then there’s presumably some sort of northward spring migration similar to monarchs and dragonflies and other things. So this is obviously very important for pollination because they’re moving those, that pollen around there over these massive distances and this can be very important for plant gene flow and all these other things.
So before I left Georgia, I’ve been working on a Georgia hoverfly biodiversity project and I’ve been looking at specimens in the Georgia Museum of Natural History in Athens there, and I found that at least 158 species in Georgia, and a huge amount of those are the eristaline hoverflies, those decomposers, and then about a quarter of them are our, you know, our predacious hoverflies. And then you have these other small groups that have, that are also, you know, have interesting life histories. But anyway, so this just illustrates there’s probably way more species that I haven’t been found. Probably the number is somewhere around 200 or even higher in terms of the number of species in Georgia. And this largely applies to other states around there.
So if you’re looking for good hoverfly identification resources, I suggest getting your hands on this field guide to flower flies of the northeastern North America. Unfortunately, there’s not one for the southeast, but it largely covers species from the southeast. And then also, I just recently published a — as Becky mentioned, I published this guide to common hoverflies of Georgia. And again, this applies to most surrounding states, just in the Southeast in general. And this has, in here, there’ll be a guide to the most common species you’re likely to encounter, and a little bit about their life histories and biology and such. So take a look at that. I’ve included a QR code here. There will also be a QR code at the very end for you to see.
Flies in Crop Pollination
Scott Clem: Just the very end of my talk, I just wanted to briefly talk about the importance of flies in agricultural pollination. So of the wild insects, bees are largely this traditional focus. And for good reason, there’s 800 species of… that move pollen quite efficiently. However, this diagram, which depicts all the other pollinators in addition to bees — so bees are in blue, and then flies are in yellow or white, and then things like beetles and wasps are in orange and red here. And then on the X, here we have our top world’s crops that have been surveyed. And what you can see is that nearly 50% of visits to a lot of these crops are achieved by hoverflies and other pollinating flies, illustrating their importance. In fact, flies are known to visit at least 72% of the world’s crops.
In the Southeast, there are several crops that depend on, to at least some extent, on fly pollination. This includes things like canola, as well as carrots, strawberries, blackberries, apples and peaches, onions, peppers, kiwi. This is just really a short list, but there’s a lot of crops out there that receive pollination benefits from flies in addition to bees. And in some cases, flies can actually be more significant.
Plants That Bring Flies to a Yard
Scott Clem: And if you’re interested in drawing in flies to your backyard, like pollinating flies, there’s a couple of fly-friendly native plants that I thought I’d throw on here. These are the ones that I tend to seek out when I’m looking for hoverflies and such. Things like mountain mint is a really good one. You get all sorts of interesting flies and many other pollinators at that one. My mom actually has a very large mountain mint plant in her backyard and every time I go home I’m always looking at that mountain mint because it’s got so many interesting pollinators on it. There’s Virginia pepperweed, which has these tiny flowers. Not necessarily all that appealing aesthetically, but it has, it is a very fly pollin… like you get lots of flies that visit this thing. Smartweeds. These have teeny tiny little flowers. You get lots of flies that visit those. As well as various asters, various pink and white asters and blue asters, different things are very fly friendly. And then finally, blue mistflower is another good fly pollinated native plant. So lots of options here. Feel free to reach out if you want to talk about these things.
Okay, and with that, I will stop my long-winded — I tend to be long-winded, so I apologize for that. But with that, I wanted to just kind of drop that if you’re interested in learning more about fly pollination, look out for my soon-to-be-published book chapter. This is in the book, Threats to Pollinator Abundance and Diversity. And the book chapter is “The Unsung Heroes: The Importance of Flies in Wild and Domesticated Pollination.” Hopefully this will be published before the end of the year. I’ve included a QR code to Common Hoverflies of Georgia, as well as a QR code to my lab here at Illinois State University, in case you’re curious what all we’re up to. All right. Well, with that, thank you so much.
Gabrielle LaTora: Wasps in the Landscape
Becky Griffin: Wow, Scott, that was amazing. I think you accomplished your goal of getting everybody, if they don’t love flies at this point, they at least understand they’re important. So I think that’s good. And all of these resources, we’re going to link to on the recordings as well. So what I’m going to do is I’m going to go jump right into our next speaker and then after that we’ll see about some questions.
So our third speaker is Gabrielle LaTora. She’s an agriculture and natural resources agent for UGA Extension in Fulton County, which is a huge job. She’s an entomologist by training and she’s passionate about closing the gap between people and their food. She works with farms and gardens across metro Atlanta and brings a practical hands-on perspective to beneficial insects. She’s an amazing speaker and a good friend and at this point, Gabrielle, I’m turning it over to you.
Gabrielle LaTora: Thank you so much, Becky. That was such a nice intro. Let me see if I can get my slides up here. Y’all can see me and hear me okay?
Becky Griffin: Yes, ma’am.
Gabrielle LaTora: All right, let’s go. So today I’m talking about wasps. Like Becky mentioned, I’m an extension agent in Fulton County, which is the county in Georgia that contains the city of Atlanta and 17 other municipalities. So we have a lot of gardens and a lot of places to look at pollinators. And I just want to give a shout out to some of my Master Gardener volunteers that are here in the audience. I saw Anne, Chris, Caroline, Jean, Kelly, Kelly, Kelly, Shirley, and Valda, my good friends. And some of these ladies are hosting some pollinator census counting events here in Fulton County on Saturday, August 22nd. So if you’re in the Atlanta metro area and you want to hang out with some like-minded folks, just reach out to Fulton County Extension and we’ll get you those dates.
So let’s talk about wasps. First, I’m going to talk about how wasps are classified and just some brief tips on how to identify them, especially versus flies. We’ll talk sort of at length about wasp lifestyles, like what are they out there doing, right? And then I’ll kind of touch on why we’re even talking about wasps today. How do they act as pollinators and why are they doing this pollination services? And then I’ll have kind of a diagram that shows you the differences between wasps and flies. I think it’s easier to mix up flies and bees, but Dr. Clem said flies are amazing mimics. And so we see a lot of similarities where they look like wasps as well.
How Wasps Are Classified
Gabrielle LaTora: So how are wasps classified? Basically just like all insects, they are in kingdom Animalia, they are animals. They’re in phylum Arthropoda, so they’re arthropods, and they’re in class Insecta, which makes them insects. Wasps are within order Hymenoptera, which you all probably know at this point includes bees, wasps, and ants. And then when we’re talking about wasps specifically, they’re going to be in suborder Apocrita. Okay. And so this separates them. You can see a wasp here in the right hand picture. This separates them from sawflies, which are very closely related to wasps, but — and sometimes people refer to them as wasps — but they are in a different suborder.
There are estimated to be over 100,000 species of wasps in the world, with maybe 10,000 to 20,000 that we have identified in North America. Of course, there are going to be many more than that that we have not identified or described.
And one really key characteristic of wasps is this narrow, quote unquote, waist. It’s not really a waist because it’s actually a constriction within the abdomen. So if you look at this picture on the right side, it’s a constriction between the first abdominal segment, which I’m hovering around with my mouse, and the second abdominal segment. So I don’t know. I mean, insects don’t have a waist, but it kind of looks like that in a way. And the scientific term for that is petiole.
Identifying a Wasp in the Field
Gabrielle LaTora: So how can we identify a wasp, especially compared with bees and maybe with flies? So they’ve got that constricted petiole. Some flies have that as well. So that you have to put some of these multiple characteristics together when you’re making an identification. But you will get very good to the point that you can look at an insect and say, like, that’s a wasp.
Like Dr. Clem said, they’re going to have four transparent or translucent wings. So I tend to, when we’re talking about identification, especially of wasps and bees, I think it’s really hard to see all four wings that they have because they actually hook the front and hind wings together, especially when they’re at rest, which is really hard to see. You can kind of see in this photo. So I would kind of use the two wings on a fly versus four wings on a bee or a wasp as kind of a secondary characteristic just because it’s really hard to see when you’re actually in the field. But just know that wasps have four wings, okay?
They have a very smooth and shiny body with very little or no hair. There are some pictures in this slideshow even that show wasps that have a few hairs, but generally they’re not going to have very much hair at all. And they’ve got this kind of slender elongated body. So I’ve got a friend who is a pollinator educator, and she likes to say that wasps look like lady superheroes in catsuits. So I think that’s a good way to think about sort of what a wasp is. It looks like, right?
And then another characteristic is they’ve got these long, graceful, straight antennae. Versus flies, which we talked about already, have these two short little stubby antennae, often with like kind of bulbous parts with like a little hair, or like a little bristle. And we’ll see some more pictures of that later. But wasps tend to have what we call thread-like antennae. So they’re kind of long. I like to think they’re very graceful and beautiful.
Ovipositors, and Why Every Sting Comes from a Female
Gabrielle LaTora: I want to make a note on ovipositors for a second, because an ovipositor is our term for the specialized organ that female insects have that they use to lay eggs. And there’s lots of different forms, shapes, functions, cool things that insects do with their ovipositors. Ways that ovipositors have evolved over time to suit a particular function or a particular lifestyle of an insect.
And why ovipositors are important when we’re talking about wasps is that they often do dual action as a stinger. Okay, so when you get stung by a yellow jacket or a paper wasp or one of our other social wasps that tend to be aggressive, it’s always a female, right, because they’re stinging you with the ovipositor, which is the egg-laying organ that only females have. So this is true of bees as well.
But there’s really, really cool adaptations in the wasp world in terms of ovipositors. Some wasps have adaptations in the body where they can basically and kind of the ovipositor and kind of curl it up inside their body. Some of them use them to bore into bark on trees and actually parasitize larvae that are inside the trees. So they do all types of cool stuff with ovipositors.
Wasp Lifestyles: Social and Solitary
Gabrielle LaTora: All right, we’re going to talk for a few minutes about wasp lifestyles. And I’ve got two categories with these different terms I’m going to talk about. So first we’re going to talk about social versus solitary wasps. And then we’re going to talk about predators and parasitoids. Okay, these categories are different, and they have different implications about what the wasps are out there doing in nature.
Social Wasps
Gabrielle LaTora: Social wasps. These are like the wasps that you think of when you hear wasps. Okay, so this is actually a very, very small number of wasps compared to all of the wasps that we have in the world. And here in North America, this is a really small fraction. These are wasps that live in structured nests or colonies with a few individuals all the way up to thousands of individuals.
And we see some division of labor in these systems. So what we call a caste system, where we’ve got different morphologies, different individuals are doing different jobs. Okay, so we’ve got queens that are responsible for reproduction. The majority of the wasp individuals in the nest are going to be workers. So they’re going to be helping to build the nest, going out and collecting food, taking care of the brood, which is the offspring. And then we usually have a small number of males whose primary responsibility is to mate.
And so we see this clear division of labor, but also some cooperation. So we see multiple individuals cooperating to take care of the brood, to do these activities like nest building, as well as defending the nest. And I’ll kind of skip to the last point here. These are the wasps that can be aggressive, that tend to be aggressive if they feel that their nest is threatened, okay? And it’s because they live in this big group, right? They have a lot at stake.
These guys are predators, and something I didn’t mention is most of our social wasps are vespids. So Dr. Schmidt at the very beginning talked about the family Vespidae, which is actually a very large and kind of cosmopolitan group of wasps that includes a lot of other wasps that aren’t social, but almost all of our social wasps are vespids. They’re in the family Vespidae. And they’re predators. So they’re going out, they’re collecting other insects that they bring back to the nest and feed to their larvae. And we’ll talk about that a little bit more in a few minutes.
Solitary Wasps
Gabrielle LaTora: Okay, compare social wasps with solitary wasps. These are insects that live alone. These are wasps that live by themselves. And I’ll kind of focus on the females because they’re doing a lot of the like really cool reproductive stuff. They’re building their nests. They’re going out and foraging for insects. They’re laying eggs and they are provisioning their offspring with prey all by themselves. Okay, we don’t see this cooperation with other individuals of the same species.
And the vast, vast majority of wasps are actually in this solitary category. They don’t tend to be aggressive. Really, the only time that they’re going to be aggressive is if they get squeezed somewhere. So like if they accidentally fly into your armpit or like they’re happened to be resting on the, um, the arm of your chair and you put your arm down or something. But in general, they’re not going to defend their nest like the social wasps will. And so this is the majority of the wasps that you’re going to see out on your flowers, either in your landscape or during the census. And so you don’t have to worry. They’re not aggressive.
So just a sort of schematic of a nesting strategy for solitary wasps. Insects in general are so diverse there’s always exceptions to the rule, okay? And so this is a broad generalization, but a female solitary wasp, this is how she’s going to reproduce.
First, she’s going to build her nest cell. And we’ll look at different nest types in just a minute, the ways that they build their nest. But she’ll build some sort of cell. The nest may have multiple cells. So she may be, she may have multiple offspring in one nest, but maybe up to a few, but they’re each going to have their own cell. Okay.
Okay. Step two, she’s going to capture and paralyze some other insect prey. And we’ll talk about that predatory lifestyles in just a few minutes. But she’s actually going to fly or crawl with that prey back to the nest cell. And if anybody has ever seen this, it’s very cool. I actually have a video from when I was in college in grad school of a potter wasp like this, carrying a caterpillar over to her wasp and feeding — over to her nest and feeding it into the cell.
So that brings me to number three. She’s going to place that paralyzed insect prey into the cell and she will lay her egg either on that insect prey or near it somewhere in that cell and then she’ll seal it up. And then she’s done. She’s like, okay, you’re on your own. I gave you some food. Good luck. And then when that larva hatches, it develops on that paralyzed insect prey. So gruesome, but really cool, I think.
Where Solitary Wasps Build
Gabrielle LaTora: And so these are some different ways that solitary wasps build their nests. They may dig some underground burrows like our cicada killers, which you might be seeing around right now or pretty soon. A lot of solitary wasps will actually build their nests out of mud. So they go and collect some dirt or some mud from out in the landscape and they build these little pots like the black and yellow mud dauber wasp. Or there’s an organ pipe wasp that builds these little pots, these tubes that have multiple nest cells, and it’ll sort of hang like in the corner near the eaves of your house. And some wasps like the grass-carrying wasps, these are really cool little guys, they’ll actually use empty plant cavities to put their eggs and their larvae inside of there.
Predators and Parasitoids
Predators
Gabrielle LaTora: Okay, our next category is sort of predators versus parasitoids. Okay. So let’s go to this section. Predators. Y’all know what predators are. Okay. Predators are insects that hunt for other insects as their prey and a lot of our wasp species do this. However, the adults are not eating the prey. They’re primarily taking that prey back to their nest cells. Whether or not they’re a social wasp or they’re a solitary wasp, they’re carrying that prey back to the nest and they’re feeding it to the larvae as the larval food source.
Some predator wasps will actually specialize on particular types of insect prey. Like you can see some common categories that I put down here below. So you might have wasps that specialize on caterpillars or they specialize on spiders. There’s actually a lot of predatory wasps that specialize on spiders, which is a lot of predators, which is cool. And then we have a lot of wasps that are generalists. So they’ll go out and capture whatever they can get that’s within sort of a reasonable size that they can pick it up and take it back to the nest.
Parasitoids
Gabrielle LaTora: Our other side of the coin for this category are parasitoids. And these guys are very similar to parasites. Okay. This is — a parasitoid is an insect that develops in or on another insect, which we call the host. And the difference between parasitoids and parasites is that when this is happening with a parasitoid species, like many of our wasp species, that host insect dies in the process of the wasp developing, versus a parasite where the host typically does not die. Okay.
60 to 80% of our wasp species out there exhibit this parasitoid lifestyle. So it’s very, very common. It’s very cool and super specialized. There are these really close evolutionary relationships between the parasitoid wasp and its host species. So typically a parasitoid wasp is only going to be out there going for like one species of host or a small number of closely related species that they have sort of co-evolved in this evolutionary arms race over millennia.
And we see a huge range of sizes with parasitoid wasps. So actually the smallest insect that we know of on Earth is a parasitoid wasp that you need a dissecting scope to see. And it’s a parasitoid of some kind of louse. And some of our biggest wasps, like our ichneumonids, the ones that the females will — certain species will use their ovipositor to bore through tree bark and lay their egg in or on the larvae of wood-boring beetles that are inside the tree. Those guys can be huge. They can be like three or four inches long. So just a lot of really cool diversity in the parasitoid wasp community.
Cotesia congregata and the Tomato Hornworm
Gabrielle LaTora: And one example — I’m not going to go too much into this because we’re getting close to time — but this is a very common species of parasitoid wasp called Cotesia congregata that you will see parasitizing your tomato and tobacco hornworms. So if you grow your nightshade crops, you probably will see tomato and tobacco hornworms, which are both very common.
This species of wasp right here, you can see this picture on the left. This is an adult female resting on the head of a hornworm caterpillar. So they’re quite small. The female will lay her egg inside of the caterpillar. That egg hatches into a larvae and they feed on the body of the caterpillar as their food source. When they’re ready to pupate, they tunnel their way out and they build these little cocoons. Okay, so these are not eggs. They’re cocoon. They’re pupae. And they’re doing this dramatic transformation from the larval form to the adult form, right? And so when the adult is fully formed inside of this little cocoon, you can see where it pops the tops off. And here’s a close-up of the adult emerging, which I just think is amazing.
And so probably if you’re a tomato gardener or any of the other nightshades, you may have already seen hornworms with this in your garden. And if you see these pupae on some hornworms in your garden, I encourage you to leave it alone because this caterpillar really doesn’t have a lot of time left. You can see it’s not looking so good. And then you’ll get, you know, 30 or 40 new wasps that are not dangerous. They’re just out there looking for hornworms to parasitize.
Why Wasps Visit Flowers
Gabrielle LaTora: Okay, so let’s talk about wasps as pollinators for a second. So we’ve talked about how the different ways that wasps reproduce, you know, through these individual nest cells or in these big, larger nests of big family groups. And all of these reproductive activities are very energy intensive, especially for our solitary wasps where the females are doing all of that stuff by themselves.
And so we’ve also established that the adult wasps are not feeding on insect prey for the most part. So what they’re doing is they’re stopping off at flowers to drink up some of that really sugary, carbohydrate-rich nectar. They may also be feeding on plant sap as well as honeydew, which is our euphemism for bug poop from insects that are feeding on plant juices. So it’s kind of the sugary, like sticky substance that wasps will feed on as well as ants and other insects.
And so this is like insect Red Bull, right? This is a super carbohydrate rich substance that keeps these wasps going and allows the females to fly out and capture caterpillars and potentially other pests in your landscape and take those back to their nest to feed to their offspring. Okay. So whether a wasp is social or solitary, or it’s a predator or it’s a parasitoid, most of them are going to be stopping off at flowers to get this carbohydrate rich substance and do this incidental pollination by accident.
Wasp or Fly? A Side-by-Side
Gabrielle LaTora: All right, my last two slides are going to be comparing wasps and flies. Okay, so just a recap of some stuff that Dr. Clem talked about already. So wasps have these long thread-like antennae. Think like graceful. Even if they have little hooks on the end, they’re kind of straight and long. They’re gonna be generally hairless. Even if they have a couple hairs, mostly they’re gonna be smooth and hairless. They’ve got this constricted waist, right? The petiole. They’re gonna have four wings, although like I said, they’ve got them hooked together most of the time except when they’re in flight, and so it’s gonna be really hard to tell that they’ve got to count off one, two, three, four, four wings. But a good characteristic that I like to use is I like to think that a lot of wasps have sort of a hammerhead shark head. Like it’s not that exaggerated, but it’s almost like football shaped, elongated horizontally. And then they’ve got their eyes kind of on the end. All right. And the eyes are small, like Dr. Clem said, too. Okay.
Compare that with our fly. You can see our hover fly right here. Flies only have two wings, but they hold them at kind of a 45 degree angle and they’ve got this distinctive shape. So they remind me of like an airplane or a spaceship, holding them out at this 45 degree angle. They may have some bristly hairs too, typically except for like the bee flies. They don’t have that fine fuzzy teddy bear hair like we see with bees. They might be kind of like more thick and bristly, but they tend to have more hair than wasps do.
And then really the way that you are going to tell this thing is a fly, in my opinion, is the head. What’s going on on the head, okay? So they’ve got this semicircle sort of dome-shaped head and what I like to call pancake eyes. I don’t know. That just makes sense in my brain. They’ve got huge eyes that cover like the majority of this semicircular dome-shaped head. And then they’ve got these two short little stubby antennae that arise from the middle of the head in between the eyes. And you can see in this picture that sometimes there’s sort of a little club or like a sort of swollen part on the bottom with one bristly hair sticking out. And so very, very characteristic of a fly if you look at the head. Okay, that’s all I got. I’m gonna unshare now and we can get to questions.
Questions and Answers
Becky Griffin: Wow, thank you so much. That was great. And I think for those who are going to be doing the census, you gave some great information. I love your enthusiasm. That made me very happy. I knew you were a woman who loved her wasps.
Are Non-Queen Females Sterile?
Becky Griffin: So we got a couple questions for you. Laura wants to know, are female non-queen wasps sterile?
Gabrielle LaTora: I assume that she’s talking about the social wasps, right? Yes, that’d be my, my thought. Yeah, I don’t know the answer to that, but my guess would be yes, they’re not reproducing in some way. So I don’t know that the exact answer to that, but the queens are going to be the ones that are doing all the reproduction.
What the Sting Is For
Becky Griffin: Okay. And what is the sting function of the ovipositor in nature? Is it to stick on a plant or tree to deposit eggs or is it a defense mechanism?
Gabrielle LaTora: That is a really good question. We think that it’s a defense mechanism. Yeah. And so it’s going to be scaring off other potential predators or at least teaching them. If I look like this, like we see a lot of warning coloration in the wasp community, right? These sort of red and black, white and black, yellow and black and white, this combination of like, wow, colors. And that is meant to say, I can sing, stay away from me. And that’s why flies are so smart. Because we see a lot of that warning coloration in their community as well, where they, through evolution, you know, they didn’t — this all happened by chance — but they discovered that, um, if they’ve got this warning coloration, then fewer predators will eat them. And then the ones that survive with the warning coloration can have more babies and so on and so forth. It’s a great system.
Becky Griffin: Yes. It’s amazing that it happens.
Gabrielle LaTora: Yes.
Do Parasitized Hornworms Keep Feeding?
Becky Griffin: So the hornworm, when is the infected hornworm keep ingesting the plant? Does it keep doing damage to your tomato plants? Is it paralyzed? Does it just slow down its metabolism? What’s going on there?
Gabrielle LaTora: Yeah, so it definitely slows down. They do, they continue to feed — the caterpillars that have been parasitized by the Cotesia wasp do continue to feed for a little bit, but they really slow down. And you could see in that picture that I post, that I had on the slide, that they’ve got these necrotic patches of dying tissue on them. And so they’re really not doing that much.
And whatever foliage that you lose after they become parasitized and that starts to develop, I think is kind of worth it to get all those wasps that are helping you keep those populations down in your landscape. And so I would even, if you’re concerned about how much the caterpillars are eating, you can pluck them off and maybe put them off in a wooded area or somewhere else. Especially if you see — if they’re at the point that you are seeing those pupae, the cocoons on the outside of the caterpillar, they’re almost dead. So yeah, I would just leave them be.
Hornets, and Why Wasps Hook Their Wings
Becky Griffin: Are hornets wasps?
Gabrielle LaTora: Yes, hornets are a small group of wasps.
Becky Griffin: And why do wasps hook their wings together?
Gabrielle LaTora: Oh, gosh, that’s a good question. I don’t remember from bug school. Do you know, Becky?
Becky Griffin: I think it’s evolutionarily, it gives them a better surface area to actually move more air, since they are evolutionarily younger than flies, I believe, and flies just have those two wings. I think evolution has given them, that’s at least what I remember. We’ll make sure that that answer is correct at some point here.
How Wasps Carry Pollen
Becky Griffin: How do wasps typically carry pollen? Where does it typically get stuck on their bodies?
Gabrielle LaTora: They’re not going to be amazing pollinators because they don’t have these hairs, right? But they, I mean, y’all will know when you go out, especially to do the census, that you see a ton of wasps on your flowers, at least I do. And there’s this huge size difference. So they might be teeny tiny, they might be big, like our paper wasps and, you know, the other social wasps that we see, but it’ll just get stuck on their body, on their legs, on their mouth parts, and then they will move it incidentally. But because they don’t, they’re not very hairy, they’re not going to be the most efficient pollinators, even though they’re visiting a lot of flowers.
Yeah.
A Small Nest with No Larvae
Becky Griffin: All right. There’s so much fun to watch. All right. One last question. Donna says that she has a small nest with two to four wasps and it doesn’t look like they’re producing larvae. What do you think she’s seeing?
Gabrielle LaTora: Producing larvae and where this nest is, because, you know, when we’ve got the potter wasps with the these little pots or the organ pipe wasps. We’re not going to see the larvae. And, you know, when I teach insect classes, I go through like, what’s the larval form of a beetle? It’s a grub. What’s the larval common name for a fly? It’s a maggot. But we don’t have a common name for the larvae of Hymenoptera because we never see them because they’re in nests somewhere. So maybe just look a little bit closer. If not, they’re probably just hanging out, trying to get enough resources to reap
Closing
Becky Griffin: And with that, I’m going to… Rich, are you there? I’m trying to launch the Q&A poll and I’m not having much luck. Okay, let me see. There we go. Thank you, Rich. All right, while we are wrapping up, I want to thank everybody for attending today. I especially want to thank our three presenters. I knew that these three would hit it out of the park and I was correct.
Transcript processed for UGA Center for Urban Agriculture / Great Southeast Pollinator Course · gsepc.org
Source: Corrected SRT (Stage 1), file GTBOP_Transcript_2026-07-21_FliesAndWasps.srt (282 blocks)