Flies don’t languish and play out the last act of Camille.
Dear Matthew Alice: Do flies get sick? I mean, considering the types of environments that flies thrive in, I have to wonder what could possibly upset their rugged little metabolisms (not counting pesticides and other man-made hazards). — Oliver McFalls, La Mesa
Why, heck, yes. Flies get sicker than...um...dogs, I guess you’d say. But not very often. It’s only logical that any creature destined to spend its life wallowing in garbage, feces, and rotting flesh must be able to handle most of what comes its way. One slow afternoon, when nothing else was going on in the lab, 1 guess, some scientists decided to count the bacteria residing on a random sampling of garbage-dwelling flies. Average population was 3.683 million per fly, with a high of 6 million. Of course, a bacterium or two will inevitably find its way inside the fly. As will viruses, protozoa, worms, and fungi. Flies not only stomp around in filth, they eat it too. (And then regurgitate it, eat it again, and again. Flies are more revolting than you ever imagined.)
Just as a nuclear weapons plant worker might get suited up to dig around in a pile of plutonium, our friend the fly is protected from its environment by its hard outer shell, its exoskeleton. The chitin-and-protein armor is tough, resistant to chemicals, and waterproof. That helps reduce the fly’s exposure to infectious microorganisms in the first place. But when they are ingested, the bug’s digestive fluids destroy most of the invaders. Others are ganged up on by cells in the fly’s hemolymph (bug blood). Some surround the microorganisms and suck them up; others cluster together and form a sort of permanent capsule around the invaders. This three-layer defense usually is enough to keep a fly feeling fit.
But from time to time, the fly is overwhelmed and heads into a swoon. They’re particularly susceptible to fungus infections. Since flies aren’t particularly complex organisms, they usually go from a lively musca domestica to musca mortissimo in short order, with only a fleeting period spent as musca not feeling so hot. They don’t languish and play out the last act of Camille or exhibit the human symptoms of whatever illness they’ve acquired. You won’t find a fly with croup or the sniffles.