MARCH
2008

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

03-13-08

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Predator Cockroaches Roam Texas Cotton Fields


The midnight rampage of predator cockroaches could be an advertising slogan for the latest horror movie. But this is no Hollywood film gimmick. Nor is it just another tall tale from Texas. Yes sir, this is real stuff.

Entomologists in South Texas have reported finding cockroaches eating the eggs of the cotton bollworm. The bollworm is a moth in the adult stage. In the caterpillar stage, the insect is a caterpillar that feeds on and damages the cotton plant. So anything that eliminates the eggs helps keep the damaging caterpillar population down.

What we have here is a beneficial cockroach! Whoa! Hold your horses just a cotton-pickin' minute. Everyone knows cockroaches are pests.

Well, a few species of cockroaches are major household pests. But most cockroaches just live their life outside of our homes and go unnoticed. In fact, about 4,000 species of cockroaches are known worldwide, and only 25 or so species are considered pests.

Most species of cockroaches live in tropical or subtropical habitats, where they feed on organic material of all sorts. Consequently, cockroaches in nature play a valuable role in decomposing things like leaves and animal feces. In addition, cockroaches also become food for other animals. So, in nature, cockroaches are beneficial organisms.

The few species of cockroaches that are considered pests have developed the habit of moving into human homes and businesses, where they feed on organic material such as cookie crumbs and leftover pizza. When this happens, we don't look at cockroaches as "nature's recyclers" but as pests.

Entomologists refer to cockroaches as "nuisance pests." This means that the insect doesn't do really bad stuff, like mosquitoes that transmit disease organisms, plant pests that destroy crops or termites that consume wood in structures. Cockroaches just foul their surroundings and produce an odor. And cockroaches are very difficult to eliminate once a population is established. Consequently, humans hate cockroaches probably more than almost any other pest insect.

So what is with this cockroach that is being touted as a beneficial insect? It is a cockroach with the common name of Asian cockroach and looks similar to that household pest known as the German cockroach. The Asian cockroach is sometimes called the flying roach because, unlike most roaches, it is an active flyer. It is also attracted to lights at night. The Asian roach was discovered in Florida in 1986 and has been expanding its range across southern states since then. It arrived in Texan in 2006.

To some entomologists, it is not surprising that a generalist feeder like a cockroach might consume organic matter such as insect eggs. Some scientists speculate that many predatory insects evolved from insects that were generalist feeders. Since cockroaches have been on earth for some 300 million years, so maybe the Asian roach is exhibiting a feeding behavior one step beyond feeding on decaying stuff.

At any rate, the Texas scientists have shown that the Asian roach consumes the eggs of the bollworm. Sometimes as much as 86 percent of the eggs placed on the plants were consumed over 24 hours. That is a very good thing, if you are a cotton grower and don't want bollworms robbing profits from your crop.

Of course, it is still a bit difficult for humans to accept the fact that a cockroach could actually be a beneficial insect. So what the researchers need to do now is figure out a way to keep the cockroaches in the cotton fields and out of houses. If history is any indication, keeping Asian roaches "down on the farm" might be easier said than done.

 

 

Writer: Tom Turpin
Editor: Olivia Maddox