JANUARY
2005

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

01-27-05

Insect Guts Alive with Bugs

The term "bug" is frequently used as a name for several types of living organisms. Many people call insects "bugs." Technically, not all insects are bugs. But some are! Insects of the order Hemiptera can be called bugs. This order includes stink bugs, squash bugs, boxelder bugs and bed bugs. These terms are known as common names. 

Other insect orders also have common names. Insects classified as Coleoptera are called beetles, Lepidoptera include butterflies and moths and Diptera are known as flies. Calling these insects bugs would be like calling butterflies beetles.

To make things even more confusing, one-celled microorganisms, especially those that cause disease, are also called bugs. At one time or another, all of us have probably caught a "bug" of this type and gotten sick.

So, do bugs of the insect type ever get bugs of the microorganism type? The answer is "Yes." Microorganisms attack insects just as they do humans. And, when this happens, the insects sometimes get sick and die. In fact, insect-attacking microorganisms are used to control undesirable insects. Such use is known as biological control.

Just as most six-legged bugs are not pests, most microorganisms are not disease-related. In fact, most bugs of both types play beneficial roles in the environment in which they live. Take our digestive system, for instance. It is filled with microorganisms. By some estimates a million million bacteria call the intestines of an individual human home.

Scientists don't understand if all of those bacteria in the human gut are beneficial but one of the most common is. Named Bifidobacterium longum, it is one of the first microorganisms to colonize the digestive tract of newborns. It ferments sugars into lactic acid, and researchers say that is a good thing. That's why some people supplement their diet either by eating yogurt or a commercial product containing lactic acid strains of bacteria. These desirable bugs are frequently called probiotics.

Such good bugs are also found in the guts of insects. For instance, termites and cockroaches frequently consume food that is a suboptimal diet. These insects eat a lot of cellulose material frequently from dead plants. The dead plant material provides a lot of fiber but very few nutrients, since their gut enzymes cannot digest such stuff. That's where the microorganisms come in. These microbes can transform the plant compounds into substances that the insect can absorb as food.

Such a relationship between animals and microorganisms is called symbiosis. This means that both creatures benefit. In this case, the microorganism gets a place to live, and the insect gets help in digesting food. This is also the case with humans and the microbes in our guts.

However, as is always the case in nature, a good thing can be thrown out of whack. For instance, humans might take an antibiotic to kill some "bad" bug, which also kills the "good" microorganisms in the gut. So, we will try to replenish with a probiotic.

The problem is even worse for some insects that must molt to grow. Take termites, for example. When they shed their exoskeleton, the inside of their foregut and their hind gut is also shed. That process takes with it the contents of both parts of the gut. Since the good microorganisms live in the hind gut, they are eliminated from the termite's body.

A termite will starve to death without the microbe helpers in its gut. So, as soon as the termite molts, it has to replenish the friendly bacteria. Termites don't have doctors or drug stores for such things, but where there is the need, there is a way. The termite simply eats some termite manure, called frass, which is sure to have a good dose of the desirable bacterial. I think I'll opt for yogurt!

 

Writer: Tom Turpin
Editor: Olivia Maddox