American Dog Tick

American Dog Tick

Common Name:

American Dog Ticks

Scientific Name:

Dermacentor variabilis


An unengorged adult female is about 3/16″ (5 mm) long, male slightly smaller. Engorged American dog tick females can get up to about 5/8″ (15 mm) long, 3/8″ (10 mm) wide. Body oval, dorsoventrally flattened (top to bottom). Color brown with whitish to grayish markings often with silvery hue on dorsal shield. Dorsal shield restricted to front half of dorsum in female, almost completely covers dorsum in male. Both larva (6 legs) and nymphs (8 legs) with red markings near eyes and lack white on dorsal shield. American dog ticks are the primary vector of Rocky Mountain Spotted fever in the United States. These ticks also transmit tularemia and can cause tick paralysis. See the nymph American Dog Tick picture on the page for ID purposes.

Places Most Commonly Found:

The engorged female drops off the host and seeks a sheltered place to lay her eggs. Over 14 – 32 days she lays egg masses totaling 4,000 – 6,000 yellowish-brown eggs and then dies. Egg hatch usually occurs in 36 – 57 days and the unfed larva crawl about seeking a host. They can survive for up to 540 days without food. After feeding they drop off the host and find a sheltered place to molt. Once they reach adult stage, they crawl up on grass or other low vegetation and wait for a host to pass. Unfed adults can survive for about 2 – 3 years. The American dog tick does not survive well indoors. If found indoors, it was probably carried in on a dog and dropped off when fully engorged. American Dog Ticks bite and are most numerous along roads, paths and trails.

Most Active Period:

The entire life cycle (egg to egg) requires more than 3 months to more than a year and both larvae and nymphs can overwinter. Larval and nymph activity usually starts about the end of March, representing those that overwintered and continues to mid-July. Nymphal activity generally predominates from June to early September. Adults become active about mid-April, peak in June, and decline until about mid-September.

Difficulty of Control:

Moderate to control in landscapes. Difficult to control when eggs hatch indoors.

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