Ticks begin as eggs and hatch into the six legged larval form. Larvae usually feed on small animals and birds, particularly the white footed mouse, which serves as a major reservoir for Borrelia burgdorferi . Larvae can acquire the spirochete while feeding on an infected host, and transmit it to subsequent hosts. Once the tick acquires the spirochete it will remain within the tick throughout its life cycle. However, female ticks do not pass the spirochete on to the next generation.
Nymphs are more likely to feed on humans than larva.
They are the principal form to transmit the disease to humans because they are most likely to feed on people, and their attachment to humans is rarely noticed due to their small size. Nymphs preferentially attach to the more hidden and hairy areas of the body, such as the groin, armpits, and scalp. Nymphs feed during the late spring and summer, detach from the host, and molt into the adult form in the fall. As a nymph metamorphoses into an adult it will become either a male or female tick. These adult ticks will preferentially feed on white-tailed deer which makes it an important reservoir species in areas of infection.