JUNE
1997

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

06-12-97

Insects And People Are What They Eat

It has been said that we are what we eat. Biochemically, that is true. Nutrients in the food we eat are the building blocks for our cells, tissues and organs. Socially, the way we eat also speaks volumes about us. The message conveyed can be good or bad. That is why mothers always remind children not to eat with their fingers and to use a napkin at the dinner table.

One way naturalists define ecological roles in nature is by the type of food an animal eats. For instance, herbivore describes cattle and grasshoppers because they eat plants. Wolves and ladybugs feed on animals, so they are called carnivores. Some creatures, like most humans and some stinkbugs, eat both plant and animal matter. Those creatures that consume both plants and animals are known as omnivores.

Regardless of the type of food consumed, it must be digested. That process is present in all animals, including humans and insects, and begins when the food is eaten. As a kid I can remember chanting, "Through the teeth and over the gums, look out stomach here it comes!" just before starting to chew away at some food item. This little ditty is descriptive of the beginning of the digestive process in humans.

Swallowing our food sends it into the esophagus, a tube connected to the stomach. The stomach holds and digests the food mass until it moves to the small intestine. There, many of the nutrients are absorbed before the remainder moves to the large intestine on its way out of the body.

In many ways, an insect digestive system is similar to that of a human. There is a mouth that leads to an esophagus that goes into a tube very similar to our small intestine, which empties into a large intestine. However, insects do not have stomachs; they have food-holding devices called crops — just like birds! And like birds, many insects also have a gizzard. The gizzard functions to grind up the food that was not chewed before swallowing. Birds and insects apparently do not have mothers who remind them to chew their food 10 times before swallowing!

Some insect plant feeders do not eat plant leaves and stems and such, but merely suck juices from the plant. They don't have a gizzard. After all, their food is liquid and doesn't need to be chewed anyway. The same is also true of some insects, such as mosquitoes, that consume blood meals from animals.

Many of the digestive juices produced by humans are also present in insects. That is no surprise. After all, insects and humans share many of the same food resources, so they would need the same chemicals for the digestive process. Now if insect mothers would remind their offspring to chew their lettuce before swallowing, they wouldn't need a crop to aid in digestion!

 

Writer: Tom Turpin
Editor: Andrea McCann