American dog tick

American dog tick (Dermacentor variabilis)
Photo © James Gathany

FEATURES
The American dog tick is also known as the wood tick. This arthropod is a parasite, mainly of mammals. The adult is about one-fourth inch long. The tick’s shield (back part of the flattened body) has white markings. The mouth has backward curving hooks and sharp jaws. The larval stage has six legs while the nymph and adult stages have eight legs.

BEHAVIORS
The American dog tick may be found statewide in Illinois. It goes through egg, larva, nymph and adult stages. Its life cycle may take three years to complete. It only feeds once at each stage but must have a meal of blood before it can develop to the next stage. This animal can go for months without feeding. The adult tends to infest large- and medium-sized mammals. The immature stages feed on all mammals but are more often found infesting rodents and rabbits. The adult dies after laying eggs. The tick is most active in late spring. It must have high humidity to live so it is often found in grassy, brushy, woody or shady areas. A “questing” behavior is used to find and attach to a host. The tick crawls to the top of a stem or the edge of a leaf and extends the front legs waiting for a possible host to come by. When it does, the tick hooks on with its front legs. The American dog tick may carry the rickettsia that causes Rocky Mountain Spotted Fever and the bacterium that causes tularemia.

​Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Ixodida
Family: Ixodidae