The Wisconsin Gardener

If I saw these anywhere near me, I would run for the hills. These are the scariest looking wasp-like thing I've even seen. We are at Allen Centennial Gardens on the UW-Madison campus and I'm with UW-Extension entomologist Phil Pellitteri to hopefully give us good news about these monsters. This is kind of a special treat if you really want to think about it that way. Oh, really? These are cicada killers, and they are a solitary wasp. They remind you of the biggest yellow jacket you've even seen. Oh, yeah. The name really describes what they are about. These things go around and attack cicadas which are the creatures that start buzzing in the trees in the middle of July through August. That raspy noise, especially late in the afternoon. Right. They dig a burrow into the ground, 5-7 inches deep. Wow. The female will paralyze the cicada. She has to fly with it or drag it, whichever she can do bury it in the ground and lay her egg. One of the fascinating things about their biology is if she puts one cicada in the hole she will lay an egg that's not fertilized that will transform into a male. If she puts two cicadas in the hole she will lay a fertilized egg and it will become a female. So the females get special treatment. It makes sense to me. This is what we would call a solitary wasp. This is not a nest. Once she provisions it and lays her eggs she has nothing to do with it. Why this is important, is solitary wasps are not aggressive because there's no nest to defend. She doesn't stick around to raise these or to protect these eggs? No, now here's what the complication is. It's big. It's scary looking. If you're in an area where these are found the males are very territorial and patrol back and forth to keep other males out. They're looking for an emerging female to mate with. That's part of their biology. The territory just to hang out and look for the female. Again, there's nothing they're protecting. They use landmarks to figure out where the territory is. The mistake is, if you walk into the area you're a new landmark and they're very curious. People misread this as being an aggressive behavior so people scream and yell that they have giant wasps nesting in their house and it'll kill the kids. This is not the way this thing works at all. Now first of all, the males can't sting. They can't? That's typical with bees. Males have no reason to have stingers. Stingers are basically modified egg laying devices. If you're a male, you don't lay eggs. That's true. Even with the females You would have to tackle one of these to get stung. It's not going to happen, because they fly very well and they'll fly away from you. They're just not interested in us, basically. Fun to talk about the cicada life cycle. I happen to think they're very, very beautiful very primitive looking. This one is what we would call the Dog-day cicada. It really fits with the July and August. They're out in the late summer. They are often associated I think of when it's time for the kids to go back to school because that's about the time it overlaps. This is the prey. Honestly, this one was stung by a cicada killer. Really? This is what she'd have to drag and put into the burrow. This has a three-year life cycle. There are Dog-day cicadas that come out every year so we always have some. People confuse this with the 17-year cicadas which we have in the southeastern part of the state. They only come out once every 17 years. That's kind of a big emergence. Cicada killers don't attack 17-year cicadas because it takes 17 years before your next meal comes by. That doesn't work. But it works very well for these. The fascinating thing to me is, as a young entomologist we did not have cicada killers in the state. I'd tell people we'd have to go to Indianapolis to find them. But with the mild winters that we've been having lately they have moved northward, and so we have cicada killers basically from Wisconsin Dells south. You need light soils to find them, so sandy areas. You don't find it in heavy clays, and the like so they can be very much localized. If you have them in the right areas you can see 15 or 20 flying at once, between males and females. That's what people misread. These guys are digging their burrows in light soils not heavy clay. Can I find them in my garden then? If it's bare soil. You don't find them in mulched areas or heavy vegetation That's one of the things that people can do to keep them away. We sometimes get them in flower beds or in planters. I you don't to put mulch on it, use landscape fabric. These won't be able to dig through it and they'll move on to somewhere else but yet you'll get the water through. So that's another adjustment. As good gardeners, of course we are all mulching so we shouldn't have a problem. Right, and we don't normally suggest to treat these. If somebody absolutely insisted I want to get rid of them the appropriate way is to dust the burrows. But as I said, if you look at their biology you can easily make the argument why do you have to kill them. Right, they're not harming anything else. No, other than cicadas, which will always be around. They'll never get all of them. So it's not a problem, just don't worry about them. Right. Thanks, Phil.