Tick Life Cycle
Ticks have four life stages: egg, six-legged
larva, eight-legged nymph and eight-legged adult. The "hard
ticks" (the group that most commonly attack people) feed once during each
Egg to Larvae
Eggs are fertilized in the fall and deposited in
leaf litter the following spring. They emerge as larvae in late
summer of that year, seeking their first blood meal. The tiny
larva crawls around the forest floor and onto low-lying vegetation
looking for an appropriate host. Their first host is generally a
mouse or other medium sized mammal or bird. Once attached, the larvae embed their
mouth parts and feed for several days. If the host is infected with
a disease such as Lyme, the tick may be infected during this
feeding. The larvae then drop off their host into the leaf litter
where they molt into the next stage, the nymph, remaining dormant until the following spring.
Larvae to Nymph
During the spring and early summer of the next year
the nymphs end their dormancy and begin to seek a host. Nymphs are
commonly found on the forest floor in leaf litter and on low lying
vegetation. Their host primarily consists of mice and other rodents,
deer, birds and unfortunately humans. Most cases of Lyme disease are
reported from May through August, which corresponds to the peak
activity period for nymphs. This suggests that the majority of Lyme
disease cases are transmitted by nymphal Blacklegged (Deer) Ticks. After feeding for
several days the nymph ticks drop off to the forest floor.
Nymph to Adult
Over the next few months the nymph molts into the
larger adult tick, which emerges in fall, with a peak in October
through November. Both
male and female adults find and feed on a host, then the females lay
eggs sometime after feeding.
Adult ticks wait for host animals from the tips of grasses and shrubs
approximately one meter above the ground. When an animal or person
brushes by the vegetation, they quickly let go and climb onto the host. Adult ticks feed on their host for five to
seven days. The female will become
engorged with blood, providing nourishment for her developing eggs.
After feeding and mating, the female tick drops into the leaf litter
where she lays thousands of eggs. She will become dormant as the
temperature drops below 40� F.
Ticks can only crawl; they cannot fly or jump. Ticks
found on the scalp have usually crawled there from lower parts of
the body. Some species of ticks will crawl several feet toward a
host. Ticks can be active on winter days when the ground
temperatures are above 45 degrees Fahrenheit.
There are two groups of ticks, sometimes called �hard� ticks
and �soft� ticks. Hard ticks, like the common dog tick and
blacklegged (Deer) tick, have a
hard shield just behind the mouthparts (sometimes incorrectly called
the �head�); unfed hard ticks are shaped like a flat seed. Soft
ticks do not have the hard shield and they are shaped like a large
raisin. Soft ticks prefer to feed on birds or bats and are seldom
encountered unless these animals are nesting or roosting in an
The most commonly encountered ticks are the American dog tick, lone
star tick, blacklegged (deer) tick and brown dog tick.
Coming soon! More content on tick biology.
Photo � 2002 Richard
Ostfeld, Ph.D., Dutchess County
Department of Health, National Institute of Health, Illinois Dept.
of Public Health.