Things That Go Zap in the Dusk

Thinking of buying one of those high-tech bug destroyers at off-season sale prices? Don't bother.

Among the many specialist groups communing on the Internet is an entomological discussion group--that is, a set of people who love to learn about insects. The group recently had a protracted exchange of information on these insect-killing devices, with enlightening results.

Back in the early 1970s, Dr. Richard Gorham, of the Arctic Health Research Laboratory then in Fairbanks, took an ultrasonic mosquito repeller to Sagwon on the North Slope. The machine emitted a kind of extremely high-pitched whine that supposedly sent mosquitoes far, far away. Gorham challenged that claim by testing the whiner at the height of mosquito season. A true scientist, he calibrated the mosquito density by exposing the back of his unprotected hand for five minutes, counting the number of mosquitoes that drew blood.

From that part of the experiment alone, Gorham was able to calculate that had he been stripped naked and tied to a post at Sagwon, he would have died from loss of blood in two and a half hours. Then he turned on the whining repeller, and found that with its help, he'd die more quickly. The number of mosquitoes biting within five minutes actually increased slightly. He was not surprised, since mosquitoes use their own characteristic whine as a method for finding mates; high-pitched whines can be the mosquito equivalent of a wolf whistle. The nonbiting male mosquitoes are most likely to be attracted, but females may also use such signals to detect happy clouds of their sisters zeroing in on food.

Gorham's brave experiment was only one test, but others in the group chimed in with similar experiences. Some even involved commercial testing laboratories. (The most notable report was of a lab in Switzerland that sent the manufacturer of an ultrasonic repeller a report stating the device was useless--whereupon the manufacturer refused to pay for the test but went on to publish advertisements using the phrase, '...as tested by [the Swiss] testing lab..') All who provided anecdotes had the same thing to report: the ultrasonic whiners are useless--at best.

The other sort of electronic insect destroyer is the more familiar bug zapper, in which an ultraviolet fluorescent lamp lures flying victims into an electrically charged grid, which then--in effect--fries them. There's no doubt that these devices kill insects; many a neighborhood lawn party has been punctuated with the frequent Zzzzist! of incinerating bugs. But the interesting information the Internet group offered was which bugs these zappers kill.

According to the group members, their tests showed that about 95 percent of the insects killed in zappers were harmless or even beneficial. The devices are ineffective against biting flies. They may attract mosquitoes to some degree, but mosquitoes have their priorities straight: once attracted into the vicinity by the light, they turn aside to find the people instead of flying on into the lethal grid.

Local results confirm that our mosquitoes are no more susceptible to electronic lures than are Outside bloodsuckers. The Alaska Lepidoptera Survey has run ultraviolet light traps in the Fairbanks area for several years. The bulk of the catch has been moths, plus some beetles, caddis flies, and parasitic wasps. Mosquitoes and other biting insects have been conspicuously absent from the traps.

Furthermore, the byproducts of bug zapping are fragments of moth wing scales (which are violently allergenic to some people) and microscopic droplets of iron and other metals from the spark. Anyone with any respiratory problems would be well advised to give bug zappers a wide berth.

So zappers are good only to satisfy entomophobes--people who hate or fear insects and are delighted by the sound of one frying. Otherwise--well, one member of the group estimated that about $40 million has been spent on useless zappers. Think of that sound as a dollar bill going up in smoke.