Of Mice and Botflies

On botflies, the white-footed mice they inhabit, and theodicy, with guest appearances by Ralph Waldo Emerson and Henry David Thoreau.

 
Ralph Waldo Emerson, I’d like a word—and bring along Henry David, too, because September is National Botfly Month, at least for white-footed mice in the Brockport Woods. Pick up a mature white-footed mouse in September and there’s a decent chance that it will carry one or more botfly larvae nestled in its groin. Each larva chews a breathing hole through the mouse’s skin, and there it lies: softly pulsating, living the good botfly life. A full-grown larva might be three quarters of an inch long and weigh one gram, about five percent of an adult mouse’s weight—equivalent to a 7.5-pound larva in a 150-pound human. Shades of Alien, although there’s no spectacular botfly explosion from the mouse’s chest, just a soft, rhythmic writhing before the mature larva tunnels out of the mouse, goes to ground, and pupates. Come spring the surviving pupae metamorphose and emerge as adults who devote their short lives solely to reproduction. Botfly eggs, which females lay near rodent burrows or runways, will hatch quickly after exposure to the subtle increase in temperature caused by a passing mouse. The tiny larvae latch onto the wandering host, usually near the nose or mouth—openings they’ll use to enter the mouse before migrating to the groin, where they’ll grow fat and happy in their warm and sheltering home.

All god’s creatures, great and small.

About those botflies. Over decades of ecological fieldwork I’ve mostly grown inured to the gruesome things that field biologists inevitably encounter, but sometimes my stomach does a small two-step at the sight of a full-grown botfly larva, gently twisting beneath its mouse-skin blanket. My digestive distress soon dissipates, but a deeper psychic angst does not. Partly it’s the ghastly physical presence of a fullgrown botfly, but there are larger issues here. “There seems to me too much misery in the world,” wrote Darwin, and for me botfly larvae represent this overabundance of suffering and pain. That’s a lot of symbolic weight for a one-gram parasite to bear, but still: that writhing mass, so foreign in its otherness, just beneath the mouse’s skin. (And yes, there also are human botflies, although they are mostly topical and their life cycle differs from that of a mouse botfly.) 

And so to Emerson and his declaration: “I will be a naturalist.” Ah, but Ralph Waldo, you were an armchair naturalist, inclined to a warm hearth and your comfortable Concord lodgings. For you an expedition into “Nature” might involve a trek across a snowy village commons—and from that congenial position you could declare, “I am impressed with a singular conviction that not a form so grotesque, so savage, or so beautiful, but is an expression of something in man the observer.” Maybe, but I’d like to drag your ghostly philosophical butt out into the Brockport Woods, hand you a white-footed mouse harboring two or three Boone and Crockett-sized botfly larvae, then ask if “Nature always wears the colors of the spirit.” Enlighten me as to what we confront in the Transcendentalist’s mirror as it reflects the image of a botfly larvae onto our “transparent eyeball(s)”? 

Perhaps Thoreau would have been better equipped to grapple with issues raised by mouse botflies, whether as metaphor or fact. As his short life progressed, Thoreau became more and more entranced with details of the natural world, with observation and collecting what we would call data, whether on the depth of Walden Pond or the phenology of plants growing around Concord—a practice that Emerson admonished him for, because it diverted his attention away from more important philosophical concerns. But Thoreau’s field studies must have exposed him to pain and suffering in the natural world, and perhaps he could have engaged with the philosophical and emotional difficulties raised by botflies, just as he acknowledged the “worms, which even in life and health, occupy our bodies.” Henry David saw the world as “savage and awful, though still beautiful,” which is one powerful way to describe mouse botflies.

 

My white-footed mouse-studies involve weighing, sexing, and marking every individual that I live-trap. I dump each mouse into a plastic bag, then maneuver it into a position where can I grasp it behind the ears, much like a kitten, and there’s usually a point in the process when the two of us are momentarily face-to-face. And sometimes I wonder: What exactly does the mouse see through those bulging, blackbrown eyes? What do I look like, and what exactly is going on in that tiny mouse-brain as it regards me from the far side of an evolutionary gulf that arose 80 or 90 million years ago, when the paths leading to rodents and primates diverged? In the words of Henry Beston, mice may be “other nations”—yet domestic rats have emotions and there must be some mouse analog to what humans call fear, similar to what I once felt when I jumped a grizzly bear dozing on a caribou carcass, an “I-am-about-to-be breakfast” jolt of adrenalin-laced panic. 

Thus my sympathy for the mice, a fondness and concern bred from decades of familiarity, some sense of shared experience, and the string of data from my scientific studies that trails across the years: sex and age ratios, reproductive timing, survivorship and movements, population fluctuations. Brothers and sisters in placenta and fur, milk and neurons: our worlds, mouse and human, turn. And so those botfly larvae gnaw away at me—figuratively, thankfully, rather than in the literal way they do in white-footed mice. 

Which brings me to theodicy, or the attempt to explain the existence of evil (such as pain and suffering) in a world created by an omnipotent, good, and just god. This is a central conundrum for Christianity. Most philosophers and theologians who have grappled with the issue have focused on human suffering—why do we deserve god’s wrath, and the shit-storm of anguish that haunts human experience?  But some people have also thought about theodicy in relation to the suffering and pain endured by non-human animals. It’s a difficult thing to do, though—at least in the Western world. As C. S. Lewis noted, “the Christian explanation of human pain cannot be extended to animal pain. So far as we know beasts are incapable either of sin or virtue: therefore they cannot be improved by it.” A 2003 academic discussion of “Animal Suffering and the Problem of Evil” offered several possible ways of dealing with the issue, none of which make much sense to me:

1. Animals do not feel pain. (René Descartes, you S.O.B.)
2. Animals feel little pain.
3. It doesn’t matter that animals feel pain.
4. Animal pain can be compensated for in an afterlife.
5. “All physical evil in the world, including animal pain, is the consequence of human sin and rebellion.”

My most polite comment to each of these possible explanations might be “Really?” but I’ll only discuss the last one, a world view best explained by the Ken Ham School of Theodicy. According to Ham (of Answers in Genesis and the Kentucky Creation Museum) everything from disease to predators and weeds did not exist prior to the Fall; before then, T. rex and wolves (and by extension mouse botfly larvae) were herbivores, somehow living peaceably in the Garden with their soon-to-become prey and hosts. But once Adam and Eve ate from the Tree of Knowledge, God cursed most everything on Earth, not just the guilty parties. This scenario posits a hanging judge sort of deity, one who not only sentences the defendant to death, but also his innocent dog. Fast forward about 1,600 years to the aftermath of the Noachian Flood, when the ark landed on the mountains of Ararat. Out hop a pair of white-footed mice, or at least a kind of mouse, presumably carrying a kind of botfly, the poor rodents’ burden of pain and suffering due expressly to Adam and Eve’s failure to heed God’s warnings. Another 4,360 years or so pass and descendants of Noah’s mice and botflies are now living in the Brockport Woods, going about their business and occasionally ending up in one of my live traps. Human angst follows.

And so theodicy seems to have reached a dead end, at least in regards to non-human animals. There is no sensible cause-and-effect theological explanation for non-human animal pain and suffering, only the obvious Darwinian one: organisms adapt as best they can to their environment, with individuals of each species pursuing their own selfish ends. Selection should favor both hardy white-footed mice that survive invasion by botfly larvae, as unpleasant as it must be, and botfly larvae that do not harm their hosts too much—and field studies indicate that this is more or less the case. If this view of life seems bleak, to me it’s far less so than a world view that attempts to marry the existence of an omnipotent, good, and just god to any of the explanations for animal pain and suffering that I mentioned above.   

But what to take away from the story of the mouse botfly and its long-suffering host, other than a slight queasiness of the stomach and far greater discomfort of the soul? I see no harmony of nature there, no Emersonian “currents of the Universal Being.” But what I do see and feel is the terrible, aching beauty of life going on, of two small creatures (one cute, the other not so much) grappling with one another across the millennia. Twenty-nine years of close familiarity with both species, of weighing and measuring and thinking—science!—has helped me understand that much.

And this sense of going on—well, we humans do that, too. We struggle with our own botfly analogs—sometimes physical, more often than not spiritual—and mammal-centric being that I am, I take great comfort in the sheer perseverance of those white-footed mice, their battles with “worms” and owl talons, fox teeth and long and bitter winters. And so I’ll give a final nod to Thoreau, coming off Katahdin: “Think of our life in nature,—daily to be shown matter, to come in contact with it,—rocks, trees, wind on our cheeks! The solid earth! The actual world! The common sense! Contact! Contact! Who are we? where are we?” Thoreau understood the basic problem, and so he wondered.