B. burgdorferi) which causes Lyme disease, the larvae may become infected and pass the bacteria on to the next stage in the tick's life cycle, the nymph.
Nymphs have eight legs and are also very small, about the size of a poppy seed. In the late spring and early summer nymphs seek a host, usually a mouse or other small- to medium-sized mammal, and feed. Because of their small size nymphs can easily go undetected and are responsible for most Lyme disease cases in humans.
If the host is infected, the nymph again has an opportunity to acquire infection with the Lyme disease bacteria. Engorged nymphs drop into the leaf litter and molt (change) into sexually mature adults. The adult ticks are active from fall to spring at times when the temperature is over 40F. The adult female feeds on large mammals like dogs, deer, or man. After mating, she drops off to lay eggs and the cycle begins again.
In Southern and Pacific coastal states the host of the larvae and nymphs is frequently a lizard-a coldblooded reptile. Certain lizards, such as the western fence lizard, are not susceptible to infection with the Lyme disease spirochete. Thus the actual infection rate of ticks varies in different parts of the country. Whereas it may be 50% (or more) in adult ticks in hyperendemic areas of the northeast, the infection rate in nymphs or adults is only 1-2% in most areas of the south and west. Thus your chances of becoming infected with Lyme disease in the northeast and certain localities in the upper midwest may be twenty-five times greater than in other parts of the country.