MARCH
2008

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

03-27-08

Download the audio of On Six Legs: MP3, WMV.

Homeward Bound has Meaning for Some Insects


In general, insects don't have homes. In fact, homelessness is a way of life for most insect species. But not all. Insects known as social insects, including bees, ants, wasps and termites, have a permanent abode. Frequently called a nest, that abode is where young insects are reared.

Home-dwelling insects leave their homes in search of food, water or building materials. Like other animals with a permanent residence that means insects must have the ability to find their way home. How animals do this has always fascinated scientists.

Wingless worker ants and termites mark a trail from the nest by depositing chemicals along the way. An insect uses these chemicals to mark a trail as a guide to the nest, in much the same way a dog uses a scent to trail another animal. Each time an insect travels back to the nest from a good food source the chemical odor is refreshed. That is why groups of ants are frequently observed moving along the same trail from an anthill to a food source. Termites exhibit a similar behavior but, because these insects stay underground or in wood, their movements are hidden from our view.

Ground travel following a marked trail is one thing, but how do flying insects such as the wasps and bees find their way around? One approach is to use the insect equivalent to a Global Positioning System (GPS). Almost 60 years ago, Von Frisch showed that honey bees used a dance to communicate the direction of a nectar source to other bees. Direction was keyed to the position of the sun.

Honey bees apparently possess an internal compass that corrects for the continuous movement of the sun across the sky throughout the day. That means the bee doesn't have to reset the sundial for each trip to the same nectar location.

But all insects that fly don't use the sun as a travel guide. In fact most don't. A more common approach to insect navigation is the use of landmarks. Such a relationship was demonstrated some years ago when digger wasps would not find their burrows if local landmarks were moved. Odor probably played a role when the wasp was on the ground, but the local landmarks established the place to land.

Scientists suggest that insects use familiar landmarks in identifying their home sites. Most entomologists that study bees and wasps have noticed that these insects seem to take a survey flight when they leave the nest or hive for the first time each day. It appears the insect is learning to recognize the surroundings before heading off in search of food.

That is the reason that beekeepers can move hives at night and still have the bees come home to the hive the next day, even though the hive is in a different location. And, for the same reason, bees out in the field during the day when their hive is moved accumulate at the location where the hive was located when they left.

Bees and wasps, apparently like humans, employ multiple strategies relative to the use of landmarks to orient to sites. We all know we can recognize familiar scenes from our past relative to places of employment or homes. Insects can do the same. Bees transported to a familiar area seem to know which way to go home.

Like humans, insects use familiar landmarks to find their way. Have you ever been traveling and noticed a landmark and said, "turn here"? Both insects and humans use beacons and landmarks in line or in the vicinity of the desired destination. "There's the tower over there; where we're going is just down the street!"

Insects learn the area and use landmarks and beacons to orient their travel to desired locations. And, at times, insects even throw in a little help from GPS systems. When it comes to travel, insects and humans are very much alike. Except insects don't have family members to remind them that they made a wrong turn!

 

 

Writer: Tom Turpin
Editor: Olivia Maddox