Adult bedbugs are reddish-brown, flattened, oval, and wingless. Bedbugs have microscopic hairs that give them a banded appearance. Adults grow to 4 – 5 mm in length and 1.5 – 3 mm wide. Newly hatched nymphs are translucent, lighter in color and become browner when they reach maturity. Bedbugs use pheromones to communicate regarding nesting locations, attacks, and reproduction. The lifespan of bedbugs varies by species and is also dependent on feeding. Bedbugs are bloodsucking insects. Most species feed on humans only when other prey is unavailable. Bedbugs are attracted to their hosts primarily by carbon dioxide, secondarily by warmth, and also by certain chemicals. Bed bugs are parasitic insects that feed exclusively on blood. Cimex lectularius, the common bed bug, is the best known as it prefers to feed on human blood; other Cimex species specialize in other animals, e.g., bugs. The name bed bug derives from the preferred habitat of Cemex lectularius: warm houses and especially near or inside beds or other sleep areas. Bed bugs are mainly active at night but are not exclusively nocturnal. They usually feed on their hosts without being noticed. They obtain all the additional moisture they need from water vapor in the surrounding air. Bed bugs are attracted to their hosts primarily by carbon dioxide, secondarily by warmth, and also by certain chemicals. Bedbugs prefer exposed skin, preferably the face, neck, and arms of a sleeping person. Although under certain cool conditions adult bed bugs can live for over a year without feeding, under typically warm conditions they try to feed at five- to ten-day intervals, and adults can survive for about five months without food. Younger bedbugs cannot survive nearly as long, though even the vulnerable newly hatched first instars can survive for weeks without taking a blood meal.