Where do fleas come from?
The most common flea found on cats and dogs is the cat flea. The most important source of fleas is newly developed adult fleas in pupae in your house. Adult fleas live and feed on animals but the female lays eggs which fall off into the environment, under favorable conditions these eggs develop first into larvae and then into pupae. The pupae contain adult fleas which lie in wait for a suitable host. Carpeted, heated homes provide ideal conditions for the year round development of fleas. The highest numbers of flea eggs, larvae and pupae will be found in areas in the house where pets spend most time such as their beds & furniture. Even though fleas may be in your house you probably won't see them; the eggs are too small to see without magnification and the larvae which are just visible migrate deep down into carpets, furniture or cracks in floors away from the light.
The flea life cycle
Although you are only able to see the adult flea, there are actually 4 stages of the life cycle. The adult flea constitutes only about 5% of the entire flea population if you consider all four stages of the life cycle.
Flea eggs are pearly white and about ½ mm long. Fleas lay their eggs on the animal, but the eggs fall off into the environment. The eggs make up 50% of the flea population. They hatch into larvae in 1 to 10 days, depending on temperature and humidity.
Flea larvae are slender and about 2-5 mm long. They feed on organic debris found in their environment and on adult flea feces, they avoid direct sunlight and actively move deep into carpet. They live for 5 to 11 days and then pupate. Moisture is essential for the survival of these immature stages of the flea. Larvae survive best in the protected environment of carpet or in cracks between hardwood floors. They thrive in warm conditions.
Following complete development, the mature larvae produce a cocoon in which the next step of development, the pupa, resides. In warm, humid conditions, pupae become adult fleas in 5-10 days. However, the adults do not emerge from the cocoon unless stimulated by vibration, carbon dioxide, or heat. Pre-emerged adult fleas can survive up to 140 days within the cocoon, during this time, they are resistant to insecticides applied to their environment. Because of this, adult fleas may continue to emerge into the environment for up to 3 months following insecticide application.
When the adult flea emerges from its cocoon, it immediately seeks a host because it must have a blood meal within a few days to survive. It is attracted to people and pets by body heat, movement and exhaled carbon dioxide. It seeks light, which means that it migrates to the surface of the carpet so that it can encounter a passing host. Following the first blood meal, female fleas begin egg production within 2 days. Egg production can continue for as long as 100 days, which means that a single flea can produce thousands of eggs.
This entire life cycle (adult flea --> egg --> larva--> pupa --> adult) can be completed in 14-21 days with the proper temperature and humidity conditions. This adds to the problem of flea control.
