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These Bugs Are On the Ball: Computerized Tracking System Shows What Pests Prefer

Entomologist observes a Colorado potato beetle's reponse to plant odors: Click here for full photo caption.

Entomologist Joseph C. Dickens
observes a Colorado potato
beetle's response to a blend
of plant odors coming out of
the tube at right. The beetle
is walking atop a servosphere.

From a distance, through squinted eyes, it looks like a vehicle driving on the moon. But when you get closer, you see that it's actually a tiny bug making its way across the smooth terrain of a servosphere—an incandescent globe the size of a basketball.

At the Chemicals Affecting Insect Behavior Laboratory, in Beltsville, Maryland, entomologist Joseph C. Dickens uses this special, custom-made equipment to figure out which stimuli attract insects.

"There are a lot of basic behaviors we can track with the servosphere. We can find out how the insect reacts to plant odors and pheromones by watching how long it will walk toward either scent, for example," says Dickens. He can also assess the interaction between chemical and visual stimuli.

The servosphere was developed by SYNTECH, a manufacturer of custom scientific equipment, after discussions between Dickens and SYNTECH president Jan Van Der Pers. The instrument took 3 years to design and build.

Entomologist uses the servosphere in conjunction with the computer program SphereTrack: Click here for full photo caption.

Entomologist Joseph Dickens
uses the servosphere in
conjunction with the computer
program SphereTrack to determine
how insects move in relation to
external stimuli such as scent
and light.

Dickens, a behavioral physiologist for insects, essentially teases the bugs with different scents and other stimuli to gauge what turns them on. "We want to know more about their internal desires," says Dickens.

To find out how insects respond to various plant odors and insect pheromones, Dickens records the path they take across the servosphere. For example, a plant odor could have a very different influence than a sexual odor on the bug's walking pattern.

On the servosphere—also called a locomotion compensator—an insect's movements are tracked by specially developed software and fed into a computer. The computer activates two motors that turn the sphere to compensate for movements of the insect, in effect keeping the bug in place as it tries to reach the object of its desire.

The device is based on the first servosphere built at the Max Planck Institute for Behavioral Physiology in Seewiesen, Germany, in the 1970s but incorporates new technology. Key to its success is a specially designed attachment through which the various scents may be funneled. The device allows air to be distributed in a consistent, even stream called a laminar flow.

Several experiments using the servosphere are in planning stages. Dickens and his colleagues have already identified volatiles released by potato plants that attract the Colorado potato beetle and a male-produced aggregation pheromone—one that attracts both sexes for feeding and mating.

When pests congregate in response to the best attractants, the possibility of catching or killing them increases. "We want to modify their behavior in such a way that we can manage them," says Dickens. These experiments should lead to development of optimal attractants combining chemical and visual signals.—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.

This research is part of Crop Production, Product Value, and Safety, an ARS National Program (#304) described on the World Wide Web at

Joseph C. Dickens is with the USDA-ARS Beltsville Agricultural Research Center, 10300 Baltimore Ave., Bldg. 007, Room 301, Beltsville, MD 20705-2350; phone (301) 504-8957, fax (301) 504-6580.

"These Bugs Are On the Ball: Computerized Tracking System Shows What Pests Prefer" was published in the February 2003 issue of Agricultural Research magazine.



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