Dog tick. Coloured scanning electron micrograph (SEM) of the head of a brown dog tick, Rhipicepha- lus sanguineus. This blood-sucking parasite of dogs can transmit to humans the Rickettsia bacteria which cause Rocky Mountain Spotted Fever (also called spotted fever or tick fever), a form of typhus. The tick's specialised mouthparts (grey, centre right) are adapted to pierce the skin of the host. It has a flattened body which swells after a meal. Ticks are relatives of spiders, and have eight legs. Ticks go through three developmental stages, feeding on different creatures during each stage. Magnification: x73 at 6x7cm size. Magnification:x120 at 4x5 inch size.