MAY
2000

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

05-11-00

Insect Mouths Have A Story To Tell

An old adage holds that we are what we eat. And as my mother often reminded me in my younger days, how we eat also speaks volumes.

Insects don't have mothers who are obligated to suggest the importance of table manners when they eat. But how insects eat does tell a story. The structure of insect mouths is related to their food and how they consume it.

An insect's mouth varies in structure from species to species and is one of the characteristics that scientists use to classify insects into groups. Most insect mouths can be categorized as one of six major types.

First, there is the chewing type. This is the type of mouth that scientists believe was the most primitive of insect mouths. Chewing insects have mandibles that cut off and grind the food—just like humans have mandibles for the same purpose. Many common insects posses chewing type mouths, including grasshoppers and crickets, cockroaches, preying mantis, beetles, dragonflies and most wasps. Caterpillars, the immature forms of butterflies and moths, also have chewing mouth parts.

Many of the insects with chewing mouths, such as grasshoppers, beetles and caterpillars, feed on living plants. Crickets, cockroaches and some beetles have to chew up dead stuff for food. Preying mantids, dragonflies, many wasps and some beetles are predators and must chew up their insect prey.

Other insects, like the non-biting flies, have a sponging type mouth. Like the house fly, these insects can eat only liquid food. Sometimes, if the item is a solid, the insect will vomit saliva on the potential food to turn it into a liquid. The liquid can then be sponged up.

Some biting flies, like horse and deer flies, have a cutting, sponging type of mouth. These insects cut the host's skin to cause blood to flow. The blood is then sponged up with the mouth parts, much the same way a surgical team would sponge up blood during an operation.

Many insects consume juices as food. These insects frequently have what are called piercing-sucking mouths. They have a hollow needle that is used to pierce plants in order to drink sap. Aphids, leafhoppers and cicadas feed in this way. Some insects use the same technique to drink blood from their prey. Mosquitoes, lice, fleas and bedbugs sup in this way.

Other insects also feed on liquids, but only if the liquids are free for the taking. Butterflies and moths have a siphoning tube for this function. The tube is called a proboscis and is generally curled up under the head of the insect when not in use. When the butterfly wants a sip of nectar, it uncoils the tube to produce a straw for sipping nectar from the flower. They also drink water in the same way.

Honey bees and bumble bees have a combination of chewing and drinking mouths. Called chewing-lapping mouths, they can drink nectar, as well as chew holes in most materials. That is how they sip nectar from a flower and chew up the wax to form the comb in the hive.

So like humans, how an insect eats sends a message. The chewers, like the caterpillars, chomp and rip their food with little thought to manners. On the other hand, butterflies sip their food in such a prim and proper way that even “Miss Manners” would be proud. Who would know that based on their eating habits the caterpillar could ever turn into a refined butterfly? Human moms take heart! There is hope for that chomping and chewing teenage son in the house.

 

Writer: Tom Turpin
Editor: Olivia Maddox