Blacklegged Tick (Deer Tick)

Ticks

Description

Adult deer ticks have no white markings on the dorsal area nor do they have eyes or festoons. They are about 3 mm and dark brown to black in color. Adults exhibit sexual dimorphism. Females typically have the area behind the scutum with an orange to red color.


Figure 1. Female blacklegged tick, Ixodes scapularis Say, questing on a stick.
CREDITS: Michael Patnaude, University of Florida




Figure 2. Male blacklegged tick, Ixodes scapularis Say.
CREDITS: Michael Patnaude, University of Florida





Figure 3. Two male and one female blacklegged tick, Ixodes scapularis Say, questing on vegetation. Only the legs are visible from the second male tick, which is on the opposite side of the vegetation.
CREDITS: Michael Patnaude, University of Florida

Lifecycle

The Blacklegged Tick (I. scapularis) is a three-host tick; each mobile stage feeds upon a different host animal. In June and July, eggs deposited earlier in the spring hatch into tiny six-legged larvae. Peak larval activity occurs in August, when larvae attach and feed on a wide variety of mammals and birds, primarily on white-footed mice (Peromyscus leucopus). After feeding for three to five days, engorged larvae drop from the host to the ground where they overwinter. In May, larvae molt into nymphs, which feed on a variety of hosts for three to four days. In a similar manner, engorged nymphs detach and drop to the forest floor where they molt into the adult stage, which becomes active in October. Adult ticks remain active through the winter on days when the ground and ambient temperatures are above freezing. Adult female ticks feed for five to seven days while the male tick feeds only sparingly, if at all.

Figure 4. Nymph-stage blacklegged tick, Ixodes scapularis Say.
CREDITS: Scott Bauer, USDA

Adult ticks feed on large mammals, primarily upon white-tailed deer (Odocoileus virginianus). Beginning in May, engorged adult females typically lay between 1,000 to 3,000 eggs on the forest floor at the site where they detached from their hosts.

Adult female blacklegged tick, Ixodes scapularis Say, engorged after a blood meal

Figure 5. Adult female blacklegged tick, Ixodes scapularis Say, engorged after a blood meal.

CREDITS: Scott Bauer, USDA

The life cycle and approximate sizes of the blacklegged tick, Ixodes scapularis Say, compared with the American dog tick, Dermacentor variabilis Say

Figure 6. The life cycle and approximate sizes of the blacklegged tick, Ixodes scapularis Say, compared with the American dog tick, Dermacentor variabilis Say.

CREDITS: Michael Patnaude, University of Florida

Mortality rates for ticks are high. Tick death is caused by density-dependent factors such as parasites, pathogens, and predators, all of which appear to have little impact on tick populations. Density-independent factors causing tick mortality include a variety of adverse climatic and microclimate conditions, which can influence temperature and humidity and have the greatest impact on tick survival. Due to their low probability of finding a host, starvation also would be a major mortality factor of ticks. Host immunity and grooming activity also may affect mortality.

Distribution

The Blacklegged Tick (Ixodes scapularis) is found along the east coast of the United States. Florida westward into central Texas forms the lower boundary, although there are reports from Mexico. The upper boundary is located in Maine westward to Minnesota and Iowa. The distribution of I. scapularis is linked to the distribution and abundance of its primary reproductive host, white-tailed deer (O. virginianus). Only deer or some other large mammal appears capable of supporting high populations of ticks. In the northeastern United States, much of the landscape has been altered. Forests were cleared for farming, but were abandoned in the late 1800s and 1900s causing succession of the fields to second-growth forests. These second-growth forests created "edge" habitats which provided appropriate habitat for deer resulting in increased populations and thus, may have increased populations of the blacklegged tick.

Footnotes

  1. This document is EENY-143, one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: July 2000. Revised: July 2004.
  2. Michael R. Patnaude, Entomology and Nematology Department, University of Florida, Institute of Food and Agricultural Sciences, Gainesville, FL and Thomas N. Mather, University of Rhode Island, Kingston, RI 02881.

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