Don't squash that bug! Cockroaches, beetles, spiders and worms may be the U.S. government's next line of defense in the war on terror.

Backed by the Pentagon, scientists are recruiting insects, shellfish, bacteria and even weeds to act as "bio-sentinels," which give early warning of biological and chemical attacks, detect explosives or monitor the spread of contamination.

At Virginia Commonwealth University, biologist Karen Kester uses bugs as "flying, crawling Q-Tips" that can check their habitats for noxious materials from anthrax to chemicals more thoroughly, cheaply, and reliably than man-made sensors.

"You look at what these animals have picked up or ingested while going about their day-to-day activities," said Kester, whose work is funded by a million-dollar grant from the Pentagon's Defense Advanced Research Projects Agency, or DARPA. The exact details of the funding were not disclosed.

"Insects haven't been used this way before. No one's ever looked at what they are naturally picking up to monitor contamination," she said. "It's more than bugs fighting terrorism. It's developing a new kind of technology to detect and map biological and chemical contaminants in the environment."

June Medford, a plant biologist at Colorado State University, said the Sept. 11, 2001, attacks on America were a wake up call for her and many other scientists who had not previously thought of researching how nature can help domestic defense.

Medford, whose work is also funded by DARPA, is genetically modifying common weeds like the ones found in sidewalk cracks to make them change color if exposed to a biochemical attack.

Her research may be the high-tech answer to the canaries that miners once carried underground to warn of toxic fumes.

"The goal is to get a plant to have a simple color change that anyone could recognize, and that the Department of Defense (news - web sites) could look down at with their satellites," Medford said.

In the event of a chemical or biological attack, first responders could better know where to don chemical suits and areas which the public should avoid, she said.

NATURE DOES IT BETTER

Despite vast advances in technology, many experts including Rajesh Naik, a biologist at the Air Force Research Laboratory in Ohio, say there are still some things nature simply does better than man.

For example, Naik said some heat-sensing beetles can detect forest fires about 30 miles away. Naik's team is trying to learn how the beetles' sensors work, in order to replicate the processes in a lab.

Other researchers are using bees' uncanny sense of smell to find explosives -- including at airports. Carried in a portable hive, the bees can detect small quantities of a host of explosives including TNT and Semtex.

Promode Bandyopadhyay, a biorobotics engineer at the Naval Undersea Warfare Center, said he examined the unique sensory abilities of dogs, fruit flies, lobsters and fish to recreate these skills with artificial sensors.

At the Department of Energy's Pacific Northwest National Laboratory, scientists Meg Pinza and Susan Thomas are hoping sea creatures from clams to worms and seaweed can help warn of and track hazardous materials in water.

Most of their recent research has focused on mollusks, which can detect minute quantities of dangerous substances because of the unique way they filter water for food.

  "It gives the warning that the contaminant or biological pathogen is present, so authorities can take measures to protect (humans)," Thomas said, acknowledging researchers still had to get the sentinels closer to a real-time response.