OCTOBER
2003

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

10-09-03

Some Insects Deserve Bad Rap

Hating insects has been a human thing for hundreds of year -- maybe even thousands of years. But not all insects deserve to be stuck with a bad-bug label. Scientists tell us that most of the million or so different species of insects cause little or no trouble for humans. But there are some species that deserve to be called "bad boys of the bug world."

Generally, bad insects fall into one of two categories: insects that harm us or insects that harm our things. Yes, when those brazen six-legged creatures help themselves to something that we claim, they've crossed the line. So we tag them with a special label. A four-letter word -- pest!

Scientists like to classify things. Most schemes used to categorize insect pests have four groups. The insects that attack us are one grouping. The insects that go for our things are divided into three groups: insects that feed on our animals, insects that feed on our plants and insects that feed on our non-living possessions.

By the way, that pest classification corresponds roughly with an ecological description of insect food habits. Ecologically, insects can be categorized as plant feeders, animal feeders or what are called decomposers, creatures that feed on dead plant and animal stuff.

So what is the worst pest insect? Scientists have developed such lists over the years. They use information like number and types of crops or animals attacked, the amount of money spent to control the pest, or reduced crop or animal yield.

Mostly scientists try to capture losses in dollars and cents, and the insect with the highest sum wins the prize as the worst pest. This is where things get sticky. How can you put a dollar value on human lives? After all, some insects are responsible for human deaths, as a result of transmission of disease-causing organisms. So different lists have different worst pest insects.

The same is true of most of our personal worst insect nominations. To crop producers, the worst insects are those that attack corn, soybeans or apples. Livestock producers are more likely to nominate flies or lice as the worst pest insects. An elevator operator will probably be more concerned about insects that attack stored grain. In other words, the insects that we are most concerned about are those that cause us the most problems.

Most people do not produce crops and animals for sale, so their choice for the worst insect might have to do with their lawn and garden. Many homeowners would nominate the Japanese beetle during the summer months. Now, however, with the appearance of the Asian ladybugs that are seeking winter shelter in our homes, that insect would receive quite a few votes for the most-hated list. But, for farmers, those ladybugs spent the summer eating aphids on the soybean crop; the insect was actually beneficial under those circumstances. As you can see, we all have our criteria for what is good and what is bad.

However, the insect that will be on almost everyone's top-10 list of worst pests is the cockroach. It seems everyone hates cockroaches, though not always for good reason. To be sure, cockroaches, under some conditions, can carry disease organisms. High cockroach populations can trigger allergic reactions in susceptible people. But, mostly, we just hate cockroaches. We hate them because they have the gall to move right into our homes a feed on stuff that falls off our tables.

Ecologists tell us that cockroaches are nature's recyclers. But that is little consolation for the homeowner who sees one in the kitchen!

 

Writer: Tom Turpin
Editor: Olivia Maddox