Don’t Kill these Killer Wasps! (Cicada Killers)

This week we are looking into a wasp that is often mistaken for an Asian Giant hornet, but the fact is that these poor creatures are everything an Asian Giant hornet is not! 

 

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Transcription:

It’s episode 49 time for this podcast where every Tuesday Japan Time I drop an episode on something whacky in the world of Entomology. We had no listener submissions for this week which means I got to choose! But there are polls on the Patreon where you yourself can vote on which insect you wanna hear about along with bonus episodes for an entirely separate series I’m writing and producing talking crazy cool news and discoveries in the world of insects. If that sounds cool to you or you wanna support the show you can hop on over to the Insects for Fun Patreon page. Now on to this week's episode. 

 

Intro: 

Cicada killers are large ground-dwelling wasps in the family Crabronidae, and most of them fall into one genus known as Sphecius. These wasps are found worldwide as you can imagine, with 21 species in the Sphecius genus but not all of them kill cicadas! That being said, the four found in the United States do. The most well known species to people in the states would be the Eastern Cicada killer scientifically Sphecius speciosus, and it got a lot of press when people had the Asian Giant Hornet scare. The reason is because the wasps are similar in size, and to someone who is freaking out, and doesn’t know how to identify wasps, they’ll just immediately think Giant wasp equals Asian giant hornet. I mean lets be honest, if you saw a massive wasp flying around and had no background in entomology you too would probably assume the worst and maybe even dial up your friends and or family for your last words. Now fortunately for listeners of this podcast I will be equipping you with the knowledge to save yourselves any such embarrassing moments. 

 

Cicada killers are large, they’re all large, usually 2 inches in length, with black or maroon bodies with yellow stripes, and reddish wings. They look scary for sure, but they actually want nothing to do with you. Pictures as usual will be available on the instagram and facebook page, but for the hundreds that prefer a verbal description here we go. The main differences between a cicada killer and an asian giant horn are the body shape and coloration. Cicada killers have a black abdomen or some other color with broken or non uniform bands of yellow. Asian giant hornets have many relatively even bands of black and orange/yellow. Also! The heads are vastly different. Cicada killers have small heads and their eyes take up the majority of the space, while asian giant hornets have big yellow or yellow-y orange heads and their eyes are more centered. Also most of the time you will encounter a male cicada killer which has no stinger, and has a longer, more narrowed abdomen when compared to an asian giant hornet. When in doubt, scream and shout, kidding, just don’t get super close and swat it. 

 

Life Cycle, and food source: 

 

The life cycle of a cicada killer begins when a female wasp mates with a male within his territory. She then begins building a nest for egg laying within soft and sandy soil, typically in full sun near trees to get easy food. The holes have to be big enough to fit a few cicadas inside so they aren’t small either. Once an adequate food supply is stored she lays an egg on the body of a cicada and then begins making a new side chamber to repeat the process. She will most likely make up to 15 chambers for eggs within a single hole, and as you can imagine that’s kind of a pain to anyone who cares about their lawn. 

 

A really cool fact about these wasps is that the females can choose the gender of the eggs they lay, which is something I’ve briefly mentioned in older episodes. The reason they do this is because it takes more females than males to create a sustainable population of these wasps, and depending on the gender more or less cicadas are required. For example female eggs need 2 cicadas in the egg chamber as opposed to male eggs which only need one. The reason is because male wasps are smaller than the females and require less to mature.

 

 Anyway, once the eggs are laid it takes a few days for them to hatch and begin feeding away on the food left for them. The cicadas aren’t actually dead either. They’ve simply been paralyzed and this keeps them alive and still, until the larvae can fully develop into a pupa. Just like all wasps, cicada killers have complete metamorphosis, and because all of it happens in the ground you would never see a larva or pupa unless you decided to dig up a nest. 

 

The larvae for a cicada killer usually takes around 10 days to fully develop and in areas with four seasons, the larvae prepare for winter by creating a cocoon underground where they will stay dormant as a pupa until the next summer.

 

Some blogs online might tell you the adults feed on cicadas too but this is actually not true. The adult wasps are pollinators and feed from flowers and on plant sap. 

 

Behaviors: 

 

Cicada killers are solitary which for us is a good thing because it means they live alone and don’t have a defense hive mentality seen with hornets and other wasps. The behaviors are actually similar to carpenter bees which we talked about in episode 37 with males being very territorial, but they’re all bark and no bite. Unequipped with a stinger, these wasps are harmless and only fight other males in aerial combat through tackling each other. The females have stingers in the form of a modified ovipositor which in simple terms is the egg laying tube, but they aren’t territorial like males and chances are you won’t encounter one.  They spend most of their time preparing their nests underground and when they are on the hunt, it’s only for cicadas. If you’re lucky you might find one mid flight carrying a cicada which is really cool to see. 

 

It’s also cool to see them digging out a nest because they can move 100s of times their own weight in soil within a few hours. The females are attracted to sandy soils or soil that is on the edges of sidewalks, concrete slabs, and building foundations. Many people spot them next to driveways or near stone wall gardens. That being said I have never encountered them in Vermont, and I had sandy soil in a portion of yard with plenty of cicadas around so I’m not sure what the deal is. I even checked a map with their sightings and known locations only to find that they avoid VT and Maine but for some reason they’re in New Hampshire? Maybe things will change with the ever changing climate. 

 

Before we move on there is one more interesting behavior seen specifically in female wasps. Sometimes conditions aren’t great for cicadas, and some areas might have less food available. In these situations female cicada killers actually go into dens made by other wasps and lay their eggs on those cicadas. Sometimes they’ll even try to add an extra cicada to the nest before the other female returns, with some taking so long that they actually get caught and evicted.

 

But in those situations the eviction is just a matter of the intruder fleeing the scene. There isn’t really a major fight or anything seriously consequential. 

 

Defenses and Predators: 

 

Now when it comes to what eats a cicada killer, it kind feels more like what doesn’t eat cicada killers. I mean everything from mice to bears, bats to birds, frogs and even other insects all snack on these large wasps. Birds will also go as far as to steal cicadas right out of their hands mid flight and the wasps don’t do anything about it! 

 

In another twist of irony and cruel fate, a different wasp referred to as velvet ants, which we'll talk about in a future episode, actually stalk cicada killers, and will lay eggs in their nests with velvet ant larvae feeding on the larvae and pupae of cicada killers. This type of interaction is referred to as parasitization which I talked about in the Just Bugs Collaboration episode. 

 

The only defenses cicada killer wasps have are their large and scary looking bodies, and a stinger, but again these wasps are not aggressive and will rarely use it which is how they get bullied by other animals so easily.