American dog ticks are oval and flattened in shape, American dog ticks are brown with whitish gray markings. The larvae of the American dog tick has six legs while the nymphs and the adults have eight legs. These extremities allow them to effectively crawl through their environment, as well as crawl in animal fur and human hair. American dog ticks can range in their size. They usually range from 5mm - 15mm in size depending on whether or not they have fed on a blood host.