AUGUST
2004

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

08-12-04

What Would a Picnic be Without Ants?

Summer is the season for picnics. Picnics are defined as pleasure parties with food provided by the participants. Generally, a lot of food! Officially, picnics are held outdoors.

There are many kinds of picnics. Picnics come in all shapes and sizes. Some are sponsored by companies, political parties or service organizations. These picnics are frequently adorned with banners and accompanied by speeches and photo ops. Other picnics are family reunions where distant cousins get reacquainted or meet for the first time. Still other picnics are private affairs with one family and a picnic basket packed with goodies.

So popular is the idea of a picnic that we even have special tables just for such things. Parks have shelters and provide outdoor grills for cooking to accommodate picnic groups.

Regardless of the type or location of the event, one thing that all picnics have in common is that insects will show up to pester the human participants. Flies and yellow jackets buzz around, picnic beetles land in the salad, mosquitoes look to extract a blood meal from the human participants and ants march across the table.

Ants are so common at picnics that some fabric designers have even included ant images on the red-and-white checkered fabric that has come to symbolize picnic tablecloths.

Ants are a very common and widespread group of insects. They are, in the opinion of many entomologists, the most successful of all insect groups. As individuals, ants probably outnumber all other animals in terrestrial habitats. 

All ants are social insects that live in colonies in nests. This means that individual ants must leave the nest and collect food for the colony. Food habits of ants vary widely. Some ants are carnivores that feed on living animals. In this case, the food is frequently of the insect type, including other ants. Some ants are herbivores and feed on plant material. Still others are omnivores and feed on a combination of plant and animal food.

So why do ants show up at our picnics? The same reason that humans show up -- food!

But how do ants find the picnic? It works this way. Certain worker ants in the colony are foragers. This means the ants leave the nest in search of food. In order to find their way back to the nest, the foragers will mark the path with a chemical called formic acid. The foragers just wander around until they encounter a food source. Then, they haul some of the food back to the nest. This is accomplished by carrying a piece in their mandibles or swallowing a morsel. The latter approach requires that the ants regurgitate when they get back to the nest. Either way, workers are recruited to help bring the food home. 

hen ants find a good food source, they quickly bring others to the location to harvest the food. It is the ant equivalent of the saying, "Making hay while the sun shines." Each ant that goes to the food source remarks the trail. So the trail to the food is constantly trod by worker ants on their way to the food or coming back to the nest.

The trail will not always be the most direct route from the nest to the food. The trail reflects the path the first worker took as she was searching for a food source. But each of the ants will follow the same trail. It would appear that ants are wasting energy by not taking the most direct route to the food source.

So what if ants aren't as efficient as we sometimes make them out to be? If ants are headed to a picnic, the scenic route might be preferred. After all, it is the atmosphere that makes a picnic fun. There are more efficient ways to have a meal.

 

Writer: Tom Turpin
Editor: Olivia Maddox