Why are cicadas showing up dead on my porch?

We get a lot of letters in our inbox, and some of my favorite inquiries are ID requests where someone also notices something interesting going on.

Here’s an example of one such question:

Your Name: Becky Boots
Your Bug Question: I witnessed a Locust emerge from the ground on the 4th of July and then shed watched as it shed its exoskeleton….I took pictures….it was a very bright fluorescent green….now, every night at least one if not two seem to migrate back to my front porch, where there is a light, seemingly to go belly up and die….only now they are a dark green and black camouflage pattern with white undersides….I read a little, but cant figure out what kind they are? I live in Iowa!

Boots cicada

Picture credit: Becky Boots

This ID request is actually pretty easy for me, because I grew up in Iowa. In Iowa, the most common cicadas are Tibicen species. They grow underground for a couple years, and there’s a generation every summer. When they emerge, they’re a very pretty lime green and then harden into a camouflage coloration.

The molting process of the cicada is a really popular subject for YouTube videos. There’s all sorts of timelapse videos and animated GIFs showing both the process of molting and coloration just after emergence.

It’s an oddly specific internet fascination, but I happen to like it because I think newly molted cicadas have spectacular coloration. Here’s what this specimen would probably look like after it’s shell hardened and it’s colors developed:

Picture Credit: Fredlyfish4, via Flikr License info: CC BY-SA 2.0

Picture Credit: Fredlyfish4, via Flikr
License info: CC BY-SA 2.0

So the cicadas Becky is seeing are most likely Tibicen cicadas. The description is rough, but this genus is very common…so I feel pretty confident about that ID even without a picture.

There’s another interesting thing going on here, though…because there are also some dead cicadas on her porch.

So what’s up with those cicadas?

Light and bugs

Insects are definitely attracted to lights, and Cicadas are no exception. My apartment is in the middle of the woods, and I get them at my lights on a nightly basis as well. In the morning, it’s not uncommon to find one or two stunned cicadas under my lights. They look dead at first, and sometimes they’re on their backs. However, they’ll fly away if I pick them up and chuck them into the woods.

To be fair this is an anecdotal account on my part, and I’m not entirely sure what’s going on. It’s possible the cicadas are a species active at dusk, confused by the lights, and go dormant during the morning. It’s also possible that they’re disoriented, and the jolt from being unceremoniously tossed helps them orient themselves.

So that’s one explanation, kind of. I also find dead looking cicadas occasionally in my parking spot, who don’t recover after being thrown. These guys have something else going on entirely.

It’s no secret that I love poorly designed animals. I had a lot of fun researching and writing about the ears of praying mantids awhile back, and I’m really happy that we get to write about another animal that has wonky habits.

…but it’s not cicadas.

Cicada Killers!

One of the important regulators of cicada populations are Cicada Killer wasps of the genus Sphecius. They’re really big wasps, only rivaled in size by a handful of other wasps if we’re going by US species. People tend to notice them flying around and digging in their yards.

Cicada killers find cicadas living in trees, sting them and then drag them into a burrow they’ve already dug. The sting paralyzes the cicada, but keeps it alive so the developing wasp larva has constant access to fresh food. It’s a tidy system which works pretty well for many wasps, and a lot of wasps have a similar lifestyle.

Pictured: Single mom doing the best she can to provide for her family. Keep up the hard work, mom! Picture credit: USFWS, via Flikr License info: CC BY 2.0

Pictured: Single mom doing the best she can to provide for her family. Keep up the hard work, mom!
Picture credit: USFWS, via Flikr
License info: CC BY 2.0

As you can see from the picture above, the Cicada Killer chooses prey that’s almost as big as she is. Cicadas are heavy, and flying is really hard work. They’re really impressive, because this would be the equivalent of me lifting…well, me, and flying away with myself. At 185 pounds, I’m not a small person and I can’t imagine how difficult this must be.

Cicada Killers are really impressive animals, but flying is really hard because physics. Objects in motion tend to stay in motion, so she needs to capture a cicada at a really high vantage point in order to transport her prey. She’ll sting the prey, drop off the tree holding her prey with her legs, and then fly as hard as she can to her burrow and then drag it the rest of the way.

Given the fact that these animals prey on something that’s as big as they are it makes sense that every so often a Cicada Killer would drop her prey by accident. So what happens when a Cicada Killer drops her prey?

Again, another YouTuber actually managed to capture what happens when a Cicada Killer loses her grip:

In the video, the Cicada Killer attempts to get a grip on her prey…and even defecates a few times to lighten her load. Unfortunately, she’s in kind of a tight spot and there’s not really a great area for her to drag the prey to and take off again. So she leaves it there, and goes off to find another cicada.

If the Cicada Killer is lucky, and manages to drop her prey near a tree, it’s not uncommon for them to drag their prey up the tree a little bit and try to take off again. Sometimes, they’re successful, but a lot of time it’s just more efficient to abandon their prey and try again somewhere else.

The Bottom Line

It’s hard to say what’s going on, because I don’t have a great explanation for why cicadas sometimes go dormant near lights. I’ve got some ideas, but neither has any hard and fast evidence behind them. I consider what I described at the beginning of this post an anecdote explained by an educated guess.

Other than dormancy, it’s possible these cicadas have been paralyzed by a specialist predatory wasp. Dead looking cicadas are really common in areas where cicada killers are found, and it’s entirely possible that these cicadas have been paralyzed by a wasp who just couldn’t handle her prey.

So about this time of year, if you’re paying close attention to the insects around you, you might just be able to witness one of Nature’s most majestic predators dropping the ball.

This entry was posted in Behavior, Ecology, Physiology and tagged , . Bookmark the permalink.

One Response to Why are cicadas showing up dead on my porch?

  1. Jessica says:

    I love how these thing look. Their mouths are so weird. I always thought it was funny to pick up the old shells and chase my sis/bff around with them while she screamed ..lol

    Like

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