Female fleas mate and start laying eggs within two days of becoming a mature adult. Averaging one an hour, they can lay hundreds of eggs in the several weeks they live. And when conditions are right, it takes only a couple of weeks for the eggs to become adults.
The only good news is that only adult fleas are parasitic. All other life stages develop off the host. The eggs, about a millimeter long, hatch in two days, or one with ideal temperatures. The white, eyeless, legless larvae seldom travel far, feeding on flea feces, dry blood and other things that collect where pets live.
The larvae develop in 10 days to a month, then spin silk cocoons that look like little dirt clods or lint balls. In the cocoons, the larvae change into pupae and then adults in about four days. And when the time is right - from less than a day to more than a year - the adult breaks out in its life-or-death search for a host.
Since fleas have to have blood to survive, treating host animals is the best way to kill fleas. Several products do this well. Many contain pyrethrins, which are safe and effective but don't provide residual control. Other over-the-counter compounds include spot-on permethrin products, which are limited to dogs and can be lethal to cats.
Veterinarians can prescribe products that give weeks of control with one application. These are applied in small amounts on the back of the pet's neck and spread over its body in skin oils. Other products come as sprays. These kill fleas on the pet within a few hours and then keep working for weeks.
Once pets have been treated, it will take a while for the fleas around them to die off. As they develop, fleas keep hopping onto the pet, which keeps "harvesting" them from surrounding areas until they've been killed.
Occasionally, people allow the flea problem to get so out of hand that they need to treat their home. In this situation, it is imperative the products used contain an insect growth regulator. Typical aerosol bombs like what most people use for a quick kill only work on adults and allow for future "hatch outs" at a later date.
Insect growth regulators can break the flea life cycle. These compounds don't kill adult fleas. But they do prevent eggs and larvae from completing their development. So any fleas brought into the area won't build up a sustaining population.
Places where pets hang out gather flea eggs and larval food. Keep these areas clean and vacuumed, and treat them to prevent infestations and protect pets and people. Use a product which works on both adults and eggs.