Deer Tick Biology
The "Deer Tick", Ixodes scapularis
Ixodes scapularis, the blacklegged tick, is often called the deer tick. While it looks similar to the dog tick, it is smaller and more rounded and lacks white markings. Adult males are very dark brown, almost black. Adult females are dark chestnut brown on head, legs, and scutum, and orange-red on the rear half of the body. Larvae are about the size of a newsprint period, nymphs are about the size of a pinhead, and adults are just over 1/16" long.
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The tick on the left is a black legged tick (deer tick). The tick on the right is a dog tick - note its white markings. The dog tick does not transmit Lyme disease. Photo courtesy of the University of Wisconsin. |
The life cycle takes two years. Adults are most active from mid-September to mid-November, but activity continues in mild weather. Some adults are found in the spring. Adults most commonly attach to large animals, such as white-tailed deer. Eggs are laid in the spring and hatch in late summer into tiny six-legged larvae. After feeding, usually on small rodents or birds, the larvae transform into nymphs.
Nymphs remain inactive until the following spring (May through July) when they seek hosts. Small mammals and birds are preferred, but they readily feed on humans and their pets. After a blood meal, nymphs molt into adults, which will seek larger hosts in the fall.
Ticks acquire the Lyme disease by feeding on infected hosts. Larvae can acquire the bacterium from infected white-footed mice, but because larvae generally feed only once, they are not likely to transmit the disease to other hosts. Because nymphs are about the size of a poppy seed, they often go unnoticed until fully engorged, and are therefore responsible for the majority of human Lyme disease cases. The American Lyme Disease Foundation reports that in highly endemic areas of the northeast, up to 25% of nymphs harbor the Lyme disease spirochete.
