Breeding fleas: it's a dog's life.

This dog doesn't bark. It doesn't bite. It doesn't even scratch. However, this "artificial dog" does provide a home for thousands of bloodthirsty fleas.

Who needs fleas? Researchers, for one. Scientists need a supply of live fleas to learn more about the physiology of Ctenocephalides felis, the flea species that causes so much misery for dogs, cats, and their human owners. In addition, pharmaceutical firms use dead fleas to produce solutions used to diagnose people who are allergic to the critters.

Jay R. Georgi of Cornell University believes his artifical dog will provide enough fleas to keep real dogs and cats out of the flea-breeding business. In the past, researchers had to collect flea eggs shed from the coats of laboratory animals. That method involved the painstaking plucking of tiny eggs from the debris at the bottom of an animal's cage, Georgi says.

The artifical dog can produce about 12,000 fleas per day, the same amount produced by 25 severly infested dogs, Georgi told scientists attending an August meeting of the American Association of Veterinary Parasitologists, held in Boston.

The artificial dog is actually an acrylic box some 16 inches square, containing 25 circular flea cages. Each cage holds about 300 fleas. An aluminum cylinder filled with cow's blood and covered with a skin-like membrane rests on top of each cage. The hungry fleas insert their mouthparts into the membrane and suck out a fresh supply of warm blood.

These flea factories are already giving scientists an intimate look at the life of a flea. Before the artifical dog, scientists had to design complicated experiments to measure the amount of blood consumed by a flea. Now, determining blood ingestion is as simple as measuring the amount present before and after a feeding session. Georgi says that female fleas drink about three times as much blood as their male counterparts, in part because females produce eggs every day.