Monday, February 20, 2012

Unsympathetic Selection

As birders, we try to spend as much of our free time as possible outdoors, often in the woods. Although we've learned a lot over the past few years, the forest is still a mostly mysterious place, full of creatures that inspire both wonder and terror in equal measure. As scientists, our drive to investigate inevitably wins out, and our desire to understand pushes us to approach those things that don't immediately make sense. Sometimes we even get lucky and our new discovery turns out not to attack us.

Such was the case during our trip to Amelia Island, FL last August, when a frightening beast of a bug flew past us and set all sorts of alarms off in our heads. This massive wasp buzzed right around in our vicinity, and temporarily sent us into panic mode. It was certainly the biggest wasp we'd ever seen, but we were more immediately concerned with staying clear of it's 5" long "stinger". We kept a safe distance from it until we watched it land on a nearby leaf, and then composed ourselves and crept nearer for closer inspection, all the time wary of what that mighty "stinger" might do to us.

We learned later that this was a Giant Ichneumon wasp (Megaryssa macrurus), and that the "stinger" wasn't a stinger at all, but an ovipositor. The precise means with which the females deposit their eggs is both nasty and brutish, and was cited by Darwin as evidence against a loving and all-powerful God:

"I own that I cannot see as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars, or that a cat should play with mice."

The female ichneumon walks along a suitable piece of wood, feeling with her antennae for any vibrations within that might signal a possible larval host. Sensing a host, she drills through the wood with her metal-tipped ovipositor. Once the host individual (most commonly a caterpillar) is exposed inside its cavity, the wasp paralyzes it, rendering it unable to move, and then proceeds to deposit her eggs inside the host. She's careful not to kill it, though, keeping the animal alive so that the young, when they hatch, can eat the living animal from the inside out. 

And that is the spectacular and gruesome truth about the ichneumon wasp. That long ovipositor may not have posed any threat to me or Maureen, but it's nevertheless the harbinger of great suffering and an instrument of unfathomable torture. It just goes to show that what nature lack in pity, it more than makes up for with awe-inspiring surprises.

Note: The ichneumon wasp was also the subject of Stephen Jay Gould's essay "Nonmoral Nature," available here


  1. Cool post! Without bugs like this ichneumon wasp, we would have much more boring sci-fi and alien movies.
    That Darwin quote intrigues me, and it's a rationalization that seems to come up a lot: "How can there be a God with so much misery in the world?"

    It's interesting because I often wonder, often taking my cues from the same amazing natural forces and creatures, how can there be so much order, structure, grace, and beauty in nature without a God? If we take misery and brutality as a sign of God's nonexistence, shouldn't we take joy and beauty as a sign of his presence?

    I'm not meaning to get preachy, just musing.
    Thanks for sharing

  2. Thanks for the comment, Laurence! I'm not going to try and tackle the age-old problem of theodicy in a blog comment (on my iPhone, nonetheless), but Darwin was commenting specifically (in this case) to a God possessing the dual characteristics of benevolence and omnipotence, which, together, he found incompatible with the existence of suffering. As for the order and structure of nature, Darwin himself provided a solution both elegant and incredibly powerful and useful. Natural selection acting over vast stretches of geological time are all that are needed - no invocation of the supernatural required

    1. Thanks Nicholas. I didn't know theodicy was even a word, but it's a good one! Thanks for teaching me something : )
      I won't try to delve in either. It's an argument with which I'm unfamiliar and, for the most part, unconcerned.
      I'm guessing the theist would argue that God demonstrates his benevolence by not using his omnipotence to force man or beasts' hand, in effect allowing free will and choice (that's of course much shakier with non-rational animals) to choose suffering or happiness, and allow for a loving relationship between God and Man that can only be fostered in freedom.
      That's doesn't apply to the world of wasps and weevils so much, but then again I guess my impositions of human emotions and reactions don't either. It's interesting stuff though, and I'm fortunately content to see no contradiction between natural selection and the existence of God.

      P.S. I'm really looking forward to the stories behind that awesome Tropicbird photo