Blacklegged ticks (Ixodes scapularis) used to be called deer ticks. They are the main tick that spreads Lyme disease in the northeastern and northcentral United States. Blacklegged ticks have a complex 2-year life cycle with three stages (larva, nymph, and adult) that can all spread Lyme disease.

Blacklegged tick larvae, nymphs, and adults each prefer to feed on certain groups of animals but all will feed on people. Larvae, which are the tiny, 6-legged, first stage, attach and feed primarily on small rodents, particularly white-footed mice, deer mice, and chipmunks. Nymphs feed on small rodents but will also attack dogs and people. Adult ticks feed mainly on deer (thus their original name), but occasionally on horses and humans. But it is the nymph that is most likely to transmit Lyme disease to people.

You can’t let your guard down when it comes to ticks and Lyme disease since the active period runs from April through September. The 2-year life cycle of the blacklegged tick is tied to the season. Eggs hatch around July, and the larval ticks are active through September, searching for a host. A larval tick will either overwinter as a larva or molt into a nymph before spending the winter. The overwintering nymphs begin activity in April, peaking in June or July, then molting into adults in autumn.

Adult female ticks will typically spend the winter living and feeding on deer (the males die after mating). In the spring, the female ticks drop off the deer to lay their eggs, after which they die. And the two-year cycle is complete.

The critical facts in this life cycle to keep in mind are that the nymphs of blacklegged ticks are primarily active from May through August, and this is the DANGER PERIOD for catching Lyme disease. Check yourself and your children for ticks after every outdoor exposure, especially after exposure in yards or other areas bordering on woods. Ticks have to be attached for several hours in order to transmit Lyme disease so early removal is crucial. Adult blacklegged ticks are tiny (about the size of a sesame seed); nymphal ticks are even tinier, about the size of a poppy seed. Protect yourselves with insect repellent or repellent-treated clothing when spending time outdoors.

If you do tick control, it is essential to begin your service and recommendations to customers in late April or early May, and then repeat during the season to maximize your control of the nymphal ticks which are most likely to feed on people. For example, you may want to apply insecticide to critical yard areas in early May and then again in July for best effect.