The American dog tick, scientifically known as Dermacentor variabilis, is a common tick found in the United States. It typically inhabits grassy and wooded areas, where it waits for a host to pass by. This tick is known for its reddish-brown color and can grow up to half an inch in size when fully engorged. These ticks are most active in the spring and summer months and are known to feed on the blood of mammals, including dogs and humans. They can transmit diseases such as Rocky Mountain spotted fever and Tularemia, making it important to check for ticks after spending time outdoors.