Nov. 16, 2005  -- As further proof that some of the tiniest critters on the planet can do wonderful things for us, scientists are asking a dinky wasp, only about a quarter of an inch long, to help alert us to the presence of all sorts of terrible things, including explosive devices, toxic chemicals and even cancer.

And what's even more remarkable, this little wasp, Microplitis croceipes, can't even sting humans. It's related to the yellow jacket and all sorts of wasps that sting in self-defense, but it uses its stinger only to insert eggs in another insect, setting off a chain reaction that scientists hope to harness for our benefit.

What makes this wasp something special is an extraordinary sense of smell. All scientists have to do is trick it into thinking a bomb is food, and bingo, we've got a bomb detector.

And that, it turns out, may not be all that difficult to do. It takes less than five minutes to train a wasp to recognize a dangerous substance.

Could Replace Dogs?

Researchers in Georgia have even developed a prototype, which they call a "Wasp Hound," that uses five wasps to sniff out various chemicals and even set off an alarm.

Glen C. Rains, a biological engineer at the University of Georgia in Tifton, and W. Joe Lewis, a research entomologist with the U.S. Department of Agriculture, see a wide range of applications for their Wasp Hound. They unveiled their invention recently in Biotechnology Progress, published by the American Chemical Society and the American Institute of Chemical Engineers.

They think the Wasp Hound may even someday replace dogs as toxic sniffers. But that's probably a long way down the road since there are still a few bugs, if you'll pardon the expression, to be worked out. But at least with a Wasp Hound, you don't have to scratch its ears.

The Wasp Hound is based largely on earlier work by Lewis, who found that Microplitis croceipes has an extraordinary sense of smell, which it uses to find food.

That discovery was of great interest to the agricultural community, because the wasp can spell death to caterpillars that feed on crops, especially corn. The wasps insert their eggs into the caterpillar, which provides nourishment to the eggs, although the process kills the caterpillar.

Scientists recognized that if they could figure out exactly how the wasps find the caterpillars, they might be able to improve their foraging efficiency, and thus wipe out even more caterpillars.

Several discoveries followed, including the remarkable finding that when the caterpillars attack the crops, the leaves of the plants release a very distinctive odor, believed to be a distress signal.

"It's sort of like an SOS," Rains says.

Five Minutes of Training

Rains and Lewis soon found that they could train the wasps to associate various odors with food, so all they had to do was produce the odor and the wasps hunkered down around a pinhole in their small cage where the odor was coming in.

The Wasp Hound, an unpretentious looking gadget that is made of plastic plumbing pipe, is equipped with a tiny camera that monitors the movement of the wasps. If they are just wandering around the gizmo, nothing happens. But if they suddenly congregate around the pinhole, the camera sends a signal to a laptop computer that can issue either an auditory or visual signal.

Since most toxic substances emit some kind of odor, the wasps can be tricked if they are presented with the odor while feeding on whatever a wasp likes to eat. The odor becomes identified with food, so even a bomb could smell like lunch to a trained wasp.

Rains and Lewis tested that with explosive chemicals buried in the soil. The wasps detected the odor of the chemicals and set off the alarm, thinking food was nearby.

Rains and Lewis found it took less than five minutes to train each wasp.

"We feed them for 10 seconds, then take them away for at least 30 seconds, and we do that just three times," Rains says.

The trained wasps spend 48 hours inside the Wasp Hound, and then they are set free to enjoy the rest of their lives, normally about two or three weeks.

Short Shelf Life

And that, unfortunately, is a big problem, and the researchers are struggling to resolve it. With such a short life span, the Wasp Hound doesn't have much of a shelf life. A new cartridge, with newly trained wasps, has to be inserted often, and they can't be stockpiled because the wasps can only be tricked for a little while.

If they smell the odor that they've been conditioned to associate with food, and they don't get any chow, they lose interest in the process rather quickly, Rains says.

So the researchers think they may have to set up a system where they could supply users with wasps very quickly. And that could take a lot of wasps.

As it stands now, each wasp is trained separately, but Rains and Lewis are working on a system that would allow them to train around 50 at a time.

And since it's easy to get them to reproduce, there should be no shortage of wasps, they say.

But the concept seems a bit cumbersome, so the future of the bomb-sniffing canine is probably secure.

Most likely, the scientists believe, there will be some applications for which the wasps are ideally suited.

"There are a few things we've been looking at," Rains says, "including food safety and some medical applications."

Some forms of cancer and stomach ailments produce odors, and wasps may be just what the doctor ordered.

"Lots of things can be detected if you know what to look for in your breath," Rains says.

If they've got to smell our breath, maybe it's a good thing that these wasps can't sting.