deer tick, Ixodes scapularis

With its abdomen engorged with a host blood meal, this image depicts a lateral, or side view of a female blacklegged,
or deer tick, Ixodes scapularis. The blacklegged tick, Ixodes scapularis, transmits Lyme disease, a disease caused by
a spiral shaped bacterial microbe, Borrelia burgdorferi. This disease is known from Europe, Africa, Asia, and in almost all
the United States. It is especially common in the Northeast, in Minnesota and in northern California. This larval tick is no bigger
than the size of the period at the end of this sentence. (look here)

Wikipedia: Ixodes scapularis