By Gino Bottino, M.D.Unique among arachnids, ticks suck blood to survive. Some are as small as a sesame seed. Like tiny vampires, they latch onto mammals, birds, reptiles, and amphibians. There are soft ticks and hard ticks. A hard tick has a hard plate on its back and is more likely to bite and feed on people and animals, transmitting dangerous diseases. Hard ticks thrive in wooded areas, tall grass, and trees and shrubs. Some, such as dog ticks, make their way indoors on humans or canines.