Predator Satiation

Polistes carolina/perplexus with Magicicada prey | Shaw Nature Reserve, Missouri

I’ve probably used the term predator satiation more often during the past couple of weeks than I have during the entire rest of my life.  Students of ecology know this as an antipredator adaptation in which prey occur at such high population densities that they overwhelm predator populations.¹  This ‘safety in numbers’ strategy reduces the probability that any given individual will be consumed, thereby ensuring that enough individuals survive to reproduce.  With St. Louis currently experiencing the appearance of Brood XIX of periodical cicadas, I’ve gotten lots of questions recently from many coworkers and friends wanting to know more about these cicadas.   Often the first question is “What is their purpose?”  My standard reply begins with a statement that they, like all living organisms, are the products of natural selection, which then presents an opportunity to explain how natural selection might result in such massive, temporally synchronized, multiple-species populations.  A few eyes have glazed over, but I think most have found my answer interesting, often even leading to further questions about where they lay their eggs, what is their life cycle, why are they so loud, how do they “do it” and select mates, etc.  Of course, as an entomologist with a strong natural history orientation, I’m always anxious to introduce people to ecological concepts, and right now the periodical cicada is providing a conspicuous, real-life example of such.

¹ Also called “predator saturation,” although this term might be misconstrued to mean that it is the predators that are over-abundant.

First the eyes...

A few weeks ago, right at the beginning of their emergence in the St. Louis area, my friend Rich Thoma and I observed predator satiation in action.  While hiking one of the trails at Shaw Nature Reserve, we heard the unmistakable shriek and cellophane-sounding wing flapping of a just-captured male cicada.  Tussling on the ground ahead of us was the cicada in the grasp of a Polistes carolina/perplexus wasp, which was repeatedly stinging the hapless cicada on the underside of the abdomen.  The shrieking and wing-flapping grew less frequent as the stinging continued, until at last the cicada lay quiet.  As we approached, the wasp spooked and flew off, but we knew it would be back—we parked ourselves in place while I setup the camera, and before long the wasp returned.  It took several minutes of searching from the air and on the ground before the wasp finally relocated her prey, but once she did she began voraciously devouring it.  As the wasp was searching, we hypothesized that our presence had altered the visual cues she had memorized when flying off, resulting in some confusion when she returned, and thus the long period of time required to relocate her prey.

...then the legs!

We watched for awhile—first the eyes were consumed, then the legs.  As it consumed its prey, Rich remarked that he bet he could pick up the wasp and not get stung—likely the entirety of its venom load had been pumped into the cicada.  Both of us declined to test his hypothesis.  We also wondered if the wasp would butcher the cicada after consuming part of it and bring the remaining pieces back to the nest.  We had seen a European hornet do this once with a band-winged grasshopper, consuming the head, then cutting off the legs from the thorax and flying away with it before returning to collect the abdomen as well.  No butchering took place this time, however, the wasp seemed content to continue eating as much of the cicada as possible—a satiated predator if there ever was one!

Leg after leg is consumed.

One eye and all six legs down, time to start on the abdomen.

Copyright © Ted C. MacRae 2011

25 thoughts on “Predator Satiation

  1. Awesome pictures!
    And speaking of predator satiation, there seems to be no sign of it in the hairy woodpecker I’ve been watching in my backyard that is fattening up like young Dinka tribesmen on milk.

  2. Incredible images Ted!!!! I wish I was in your part of the state to witness all this activity. Last year in the Smokey Mountains I witnessed a European Hornet tearing apart a Robinson Cicada. I was fascinated by the process.

    • There are supposed to be 17-year cicadas up in northwest Missouri this year – haven’t seen them? There will be another 17-year brood up there in 2015, though I don’t know how it’s size compares.

      • We have a few periodicals flying around one of our farms, but nothing even close to what you guys are experiencing on your side of the state. We have dozens, compared to your millions. I hope the 2015 brood proves to be huge and entertaining!

        • It’s amazing how patchy the distribution is. The weekend before last I was in northern Arkansas – I stayed in Salem, where the cicadas were more numerous than I’ve ever seen anywhere, and just 30 miles down the road in Calico Rock they were completely absent.. Someone who lives in Cape Girardeau also said they haven’t seen them there. I would imagine with the growing interest among citizen scientists that we’ll see much more precise maps based on this year’s data.

  3. Great pics. I once watched a mantis eat off all eight legs of a tarantula then left the thing as a live body sans pes. Something about the arthropod drumstick I guess.

  4. Great post. I guess I’m a bit surprised the wasp consumed so much — I had thought that as adults they don’t need to ingest a lot of protein, and mostly eat nectar. But maybe the cicada deliciousness was being stored in a crop to feed to larvae later – social wasp, right?

    Years ago, on a sidewalk in Oakland CA, I watched a yellow-jacket subdue a huge fly – looked like one of those big hairy ones, forget the family name. Anyway, they were about the same size and there was a titanic struggle with buzzing and grappling before the yellow jacket won. Then, even from where I was standing, I could hear the crunch as the mandibles snipped through the exoskeleton of the fly to butcher it up into pieces. It was one of the most gruesome and horrifying spectacles I’d ever seen.

    • Thanks Margrit. It surprises me too, but at the same time I imagine the constant job of searching for, subduing, and bringing back prey to provision the nest is energetically quite expensive – if there is surplus available the extra nutrition can certainly be used.

      Your experience with the yellow jacket sounds similar to my European hornet experience – gruesome? Yes. Horrifying? Yes. A mind-blowingly awesome spectacle to witness? Absolutely!!!

  5. I thought social wasps didn’t sting their prey?

    Also I was surprised a wasp could cut through armor like that. We (or at least, I) usually think of Polistes as dainty, graceful things that only pick off soft-bodied caterpillars as such, while the robust Vespula and Dolichovespula go after all manner of bees, beetles, large spiders, and other formidible, well-armed prey. Clearly that’s not always the case…

    And btw I’m so jealous I would have to stay here for more than a decade for the next big cicada brood. Enjoy every decibel while it lasts!

    • I too have always thought of Polistes as fairly non-aggressive wasps, but long before I knew what they were called I knew these orange ones by their “mean” reputation.

      I was really anticipating this cicada brood, and I’ve had even more fun with it than I thought I would. They seem to be starting to wind down, so while most around me are saying “finally!” I’m feeling a little depressed.

      • Reds are very aggressive. I was chased out of my yard by one. It was in the grass, I came at it with lawn mower thinking noise/vibration would drive it off. It intentionally flew diagonally above the mower straight towards my face. It absolutely knew what was what. In two seconds I was across the street. The wasp controlled the yard. Another time I hit a clothes line pole (tubular metal) with a running mower. Out came five (5) angry reds hovering close to my face. I yelled “NO” and against all reason, I was not stung. It wasn’t that they feared me when I yelled no, it was more like the old story about man and dominion over the animals. Don’t push that idea very far, however, it has occasioned many serious injuries and deaths—look at the snake handling churches in Tennessee and Kentucky. Reds are very, very hostile and the sting is quite severe. I saw electrician claim it hurts worse than a 460 volt shock. I had one red incident as a boy and screamed for seven (7) hours. These are medically dangerous, without being “hyper-allergic.” Yes, the venom sac would have largely been depleted. That’s why misguided persons claim a cicada killer sting is mild, thy took it soon after its poison was discharged.

  6. Great photo series! I’ve watched a Polistes butcher a grasshopper. The hopper was still very much alive and attempting to be mobile as the wasp removed a femur. An amazing amount of strength in wasp mandibles relative to their body size.


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