Macroscopic dorsal view of female blacklegged, or deer tick, (Ixodes scapularis), about the size of a sesame seed displayed on laboratory light box. These ticks are responsible for the transmission of Lyme disease, the most common tick-borne disease in the northern hemisphere and which can be deadly if not properly treated. Ticks belong to an order of arachnids and possess eight multi-segmented legs legs which are adapted for climbing and clinging.