The wasps are trained with sugar water by using the classical conditioning techniques made famous by Pavlov's dogs. Rains says the wasps are sensitive to a host of chemical odors, including 2,4-DNT, a volatile compound used in dynamite.
To do their work, five wasps — each a half-inch long — are placed in a plastic cylinder that is 15 inches tall. This "Wasp Hound," which costs roughly $100 per unit, has a vent in one end and a camera that connects to a laptop computer.
When the wasps pick up an odor they've been trained to detect they gather by the vent — a response that can be measured by the computer or actually seen by observers.
Lewis says the wasps, when exposed to some chemicals, "can detect as low as four parts per billion, which is an incredibly small amount."
