The photograph shows two common U.S. tick species: the blacklegged tick (Ixodes scapularis) and the American Dog Tick (Dermacentor variabilis)

Top row, from left:

blacklegged tick larva, nymph, adult male, adult female.

Bottom row, from left:

dog tick- adult male, adult female

For scale- millimeter ruler, poppy seed on ruler; to right of ticks, sesame seed