Spring is just around the corner and the signs are all around. The days are warmer, flowering trees are growing buds and fleas are hopping across the lawn.

Yes, fleas are a sign of spring.

"Fleas populate best in warm, humid conditions," said Nancy Hinkle, an Extension Service entomologist with the University of Georgia College of Agricultural and Environmental Sciences. "That's why you don't notice fleas in the height of the summer or in the winter."

Flea larvae develop outdoors in the soil. Spring's heavy rains can drown them, and summer's heat and low humidity can dry them out. Winter's dry freezes can kill them, too.

"When temperatures moderate in the fall and spring, flea larval survival improves," Hinkle said. "That's when people start fighting fleas in their homes and on their pets."

Most Fleas Are Cat Fleas

Of the fleas on our pets, 95 percent are cat fleas.

"Cat fleas are found in North America, and dog fleas are found in Europe," Hinkle said. "Although they're different species, they look almost identical."

The main distinguishing characteristic between the two types is only visible under a microscope.

To survive, all fleas have to have an animal host of some kind.

"As long as dogs and cats are around, fleas will be attracted to them. But when the only warm bodies present are humans, fleas will take whatever is available and start biting," Hinkle said. "Fortunately, they don't survive well on human blood and won't be able to reproduce, so eventually the population will die out."

Pet-free Homes Can Still Have Fleas

Even if your home is pet-free, you can still have fleas. Cat fleas also live on stray dogs and cats and wild animals like raccoons and opossums.

"Cat fleas have been found on several dozen mammals," Hinkle said. "Frequently wild or stray animals find shelter under homes or outbuildings. When the animal abandons the site, the fleas are left behind."

The starving fleas then crawl up through cracks in the subflooring searching for a host, Hinkle said.

"For several reasons, some people are more attractive to insects than other people are," Hinkle said. "It can be something as simple as a compound in their perspiration. That's why some people attract blood-feeding insects like mosquitoes and fleas more than other people."

On the other hand, some people are just more sensitive to the flea's bite.

People and Pets Can Be Allergic

"While some people can hardly feel the bite of a flea, others experience the bite as a severe irritation," she said. "This is an allergic response to the allergens in flea saliva and can result in brief irritation or prolonged itching."

In some cases, dogs and cats can be allergic to flea bites, too.

"In flea-allergic pets, the bite from a single flea can cause a severe response," said Hinkle. "In addition to controlling fleas and eliminating your pet's exposure to them, you should have your veterinarian refer you to a veterinary dermatologist."

At UGA, Hinkle is working to develop integrated pest management of fleas by combining habitat modification and other control strategies.