Dear Matthew Alice:
In the hallway in my condo complex. there is one shady section in which the air is thick with hovering little gnats. They are very annoying. But they never seem to bite or Sling anyone. What do they do? What do they eat? Do they sleep? Where do they go at night? What enjoyment can they possibly gain from flying around in the same place all day? Please help.
R. Betz, Rose Canyon
It will be no surprise to hear that your hall loiterers are from the group known as syrphid or hover flies. On the Matthew Alice annoyance scale, they hardly register at all. Are yours some mutant strain that travels with little ghetto blasters or makes rude comments to women as they come in the building? When I consider some of the neighbors I've had over the years, all, ostensibly, from the group homo sapiens ... two late-night-party-throwing Neil Diamond fans who owned four spiteful, raucous chihuahuas; Mr. Guns-and-Motorcycles, who inspired the rest of us to form a Neighborhood Watch committee just to keep an eye on him; a middle-aged woman in primal-scream therapy .... If hover flies get you riled up, maybe your past has lacked a certain amount of color.
Be that as it may, the lives of these little bugs are simple enough. Eat and be eaten constitute their daily reality. Hall-hovering is their effort to avoid the second of these and to escape the sun on a hot day. I'm sure you've noticed the flies are most likely to appear during a heat wave. Ordinarily, syrphid flies hover under shady trees so their movements will be less noticeable to birds and other predators. But as man invades the natural landscape, hover flies have taken advantage of new opportunities and are just as content to hide out in a shady condo. If today's wildlife were to adopt a license-plate motto, it would definitely be "Adapt or die."
Adult hover flies are strictly vegetarians.
They don't bite you because they have no stinging apparatus and because blond is not on their menu. They much prefer plant carbohydrates — nectar, pollen, that sort of thing. At egg-laying time, they're partial to wild fennel and other plants that attract aphids. As for nightlife, hover flies aren't very good partiers. Come dark, they would rather sleep under some protective covering. Check out the upper comers of your hallway, when: the walls and ceiling meet. If they haven't escaped sometime in the evening, you may find them snoozing there. And as for what fun there is in hovering, the only payoff is surviving another day. I can sympathize.
Why syrphids hover is an elusive question. But the habit certainly has some social/reproductive or survival benefit. Bug motivations are not the stuff of which tangled Freudian theories are made. The flies seem to have an acute visual sense and a good feel for how far away they are from one another (and from you). If you approach a group slowly, the whole mass will move away as a unit, nobody bumping into anybody else or losing his place in the formation.
I know this is an unlikely scenario, but if you were to scrutinize a hover fly closely, you'd see that it's actually quite colorful. Its body is brightly marked with black and yellow bands, much like a bumblebee. And if the fog of bugs is truly aggravating to you, perhaps you might tum your attention to the real problem: your neighbors who leave the front door open and let in the flies in the first place.