SEPTEMBER
1993

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

9-23-93

Ants are the Agriculturalists of the Insect World

Agriculture is generally thought to be one of the crowning achievements of the human animal. Domestication of animals and growing of crops has facilitated development of human civilization as we know it.

Lest some of us are tempted to take those hands with the opposing thumbs and pat ourselves on our collective backs consider this: Long before humans were farming, ants had mastered the art.

One widely known group of ants is called harvester ants. These ants live on grass seeds that they store underground. Not only do they store their food, but if the seeds get wet, the ants bring them to the surface and let them dry. This behavior prevents germination, which would ruin the seeds as a food source for the ants. It is the food storage behavior of this ant that attracted the attention of King Solomon during biblical times and prompted him to command, “Go to the ant thou sluggard, consider her ways and be wise.”

Several species of ants use sugar as a food source. These ants frequently get sugar from the honeydew of aphids. Worker ants seek out aphids on plants and, by stroking their antennae, get the aphids to excrete a drop of honeydew. The honeydew is then picked up and carried to the nest, where it is used as food for the young ants. The process is not unlike a dairy farmer milking a cow. Consequently, aphids are sometimes referred to as ants' cows.

Some of the ant dairy farmers are so possessive of their cows that they actually protect them from harm. For example, ants that tend pecan aphids protect them from parasitic wasps that would destroy the aphids — sort of the insect equivalent of a shepherd protecting the flock from wolves.

Some ants even herd their cows and move them to greener pastures when necessary. Such is the case with the cornfield ant and the corn root aphid. These ants move the aphids from plant to plant during the growing season.

The real agriculturists among ants are known as the leaf cutters. These ants live in America and are very numerous in the tropics of South America. They make large underground nests. Workers cut leaves and bring them back into the nest. The leaves are chewed up and the resulting leaf and digestive enzyme mixture is placed in beds in the nest, where a fungus grows. The ants harvest the fruiting bodies of the fungus and use it as food. These ants have some workers that act as gardeners, keeping the fungus beds free of other fungi and bacterial growth.

So important is the fungus to the leaf cutter ants, that when a queen leaves an established colony to establish a new nest, she carries a starter culture with her. The process is similar to that of pioneer farmers bringing plants and livestock with them as they headed to settle the new lands of the United States.

Humans might have perfected farming, but the insects have no doubt been at it longer.

 

Writer: Tom Turpin
Editor: Andrea McCann