I confess, sickly people repulse me. The blame for some of this aversion lies with my upbringing. While the stomach flu and chicken pox were treated with maternal tenderness, I nevertheless inferred that falling ill was a sign of weakness. My mother was never bedridden and 
I can’t remember my father ever calling in sick, so I surmised that missing a day of school was a kind of failure, evidence of a delicate constitution hardly befitting a young man. But my internalized message does not compare to the one assimilated by my wife through her Midwestern, Protestant upbringing. Around her house—and presumably in the environs of Illinois farms—sickness was indicative of a potentially serious character flaw (on par with falling asleep on the couch while watching football). But familial messages aside, there are good evolutionary reasons for not associating with feeble folks. With respect to selecting mates, the infirm are bad genetic bets. And in terms of survival, there’s a good reason to avoid pallid people—they’re often infected with a communicable pathogen. All of this goes to explain, if not excuse, why I wasn’t all that keen on spending time with my university colleague Cheryl.* I’m neither a shallow cad who judges people based on their looks, nor an intolerant lout burdened with psychological baggage. I’m a well-adapted organism.

Horn flies are truly loathsome insects. They lay their eggs, and spend the maggoty portion of their lives, in fresh cow dung. The size of a small housefly, an adult feeds on blood up to twenty times per day, favoring the capillary-rich tissues at the base of a cow’s horns. Hence the insect’s name. This is not to say, however, that the flies are found only on their host’s head. When hundreds (in some cases more than ten thousand) of these insectan vampires are seeking a meal, the best spots are quickly occupied. So the back and sides of cattle become peppered with hungry—and horny—flies. Females lay up to two hundred eggs in their lifetimes, and the insect can crank through ten generations a year in warm climes, such as Louisiana. That’s where I met the horn fly, while studying for my doctoral degree in entomology at Louisiana State University. Although my dissertation research concerned a less noxious creature (the southern green stinkbug, which, despite its name, emits an odor reminiscent of cut grass), I was oddly attracted to these repulsive flies. They had a gritty, unapologetic, blue-collar authenticity to their lives. One had to respect a creature that had evolved the capacity to live its larval life in a pile of shit and spend its adulthood taking blood from an animal a couple of million times its own size.

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