Tom Turpin
Professor of
Purdue University







How Many Bugs Could a Bug Zapper Zap?

The approach of the lazy, hazy, crazy days of summer is always accompanied by booming sales of bug-killing devices. That's because the hot summer nights and days are perfect for cold-blooded insects. Lots of insects mean lots of human encounters with insects. And that translates into human attempts to kill insects.

For centuries, we humans have brushed, swatted and stomped the six-legged creatures that get in our way. Since World War II and the development of insecticides, we have added chemicals to our bug-killing arsenal. Killing insects has become as much of a summer ritual as lemonade, suntan lotion and family vacations.

We like to kill insects so much so that we invest our hard-earned money--millions of dollars each year--on products to help do the job. An old-fashioned flyswatter still works, but in today's high-tech society we would rather use gizmos and gadgets.

One of those gadgets is the electric bug zapper. Bug zappers are based on the attraction of night-flying insects to light, especially ultraviolet light. And when the insect arrives at the light, it gets electrocuted or zapped!

Exactly why some insects are attracted to light is debated by scientists. Most agree that artificial lights interfere with insect night behavior. One theory is based on the idea that night-flying insects navigate according to light from the moon or stars. Another idea is that insects fly to holes on the horizon, such as between trees, which have a higher light intensity. Either way, artificial lights foul up the system.

Entomologists have used this attraction to light to capture insects in traps. Such traps use a light and a series of vertical fins over a funnel that lead to a container. The insects headed to the light get diverted into the container. The traps can be used to collect insects to gain specimens, to determine presence of species or to estimate populations.

Bug zappers work in the same way, except the insects are killed by the electric grid. How well do bug zappers work to eliminate unwanted insects? Hold on to your hat. They don't! No research to date has shown that light traps help reduce damage caused by insects.

But wait a cotton-pickin' minute. How can killing all those insects not help out, even just a little bit, in the battle of the bugs? Think about it this way. Most of the insects killed by the light trap aren't pests. They are insects that just happen to be attracted to the light.

To be sure, some of the insects killed in the trap are pests. For instance, June bugs. These insects lay eggs that develop into white grubs in the lawn. But the problem is that the light trap attracts more beetles than it ends up killing. The result is that more beetles end up laying eggs in the vicinity of the trap than would have had the trap not been there. So while some beetles are killed, more grubs are found in the lawn.

What about mosquitoes? Some mosquitoes are killed by light traps, but, unfortunately, male mosquitoes are more likely to be attracted to light than are female mosquitoes. And it is those biting female mosquitoes that we really want to kill. In addition, several species of midges are also killed in light traps. Midges resemble mosquitoes but don't bite. So a light trap does not eliminate a biting mosquito problem.

So how many bugs does a bug zapper zap? Thousands per night on warm summer days. But remember, you aren't solving any insect problems by using a bug zapper. You just feel better for having killed a few thousand bugs!


Writer: Tom Turpin
Editor: Olivia Maddox