Fleas
Egg -- The white, oval-shaped egg is about 0.5 mm long.
Larva -- Varying in length from 4 to 6 mm when mature, flea larvae have slender, white, cylindrical, legless bodies with 10 to 12 moderately long setae on each segment. The head is pale brown and has no eyes.
Pupa -- Pupae develop in dingy white, oval, silken cocoons about 4 mm long.
Hosts -- Practially all warm-blooded animals are subject to attack by fleas. Each species of flea, however, usually feeds on a limited number of specific animals.
Damage -- Flea bites cause a persistent, annoying itch. Though some fleas, especially rat fleas, may transmit disease such as endemic typhus and bubonic plague, most fleas are not vectors.
Life History -- Fleas continue to feed and breed throughout the winter but often do so at reduced rates. Females mate and lay eggs on the host from which a blood meal is taken. Eggs typically fall off host animals and hatch in 2 to 14 days. Outdoors in lawn areas or pet quarters, larvae generally feed on excrement from adult fleas, rodents, and domestic pets. Larvae also survive well indoors on organic debris in carpeting or overstuffed furniture. After developing for 1 to 50 (but usually 2) weeks, larvae spin cocoons and pupate. Under favorable conditions, a new generation of adults emerges 1 to 3 weeks later. An entire life cycle may be completed in as few as 2 or 3 weeks, but several months to 2 years may elapse if conditions are unfavorable.
Adult fleas cannot lay eggs without first feeding on blood. Adults may live 1 to 2 years without a blood meal. Temperatures of 18° to 20°C (65° to 80°F) and a humidity of about 70 percent are optimum for flea development.