Mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva - this is what causes the red bump and itching. A more serious consequence of some mosquito bites may be the transmission of serious diseases. They also can transmit several diseases and parasites that birds, dogs and horses are very susceptible to. Over 200 different species of mosquitoes live in the United States, all of which live in specific habitats, exhibit unique behaviors and bite different types of animals. All mosquitoes share some common traits, such as a four-stage life cycle. After the female mosquito obtains a blood meal (male mosquitoes do not bite), she lays her eggs directly on the surface of stagnant water. The eggs hatch in two to three days and a mosquito larva emerges. The larva lives in the water, feeds and, after four to ten days, develops into the third stage of the life cycle called a pupa . The pupa also lives in the water, for another day or two but no longer feeds. Finally, the mosquito emerges from the pupal case and the water as a fully developed adult, ready to bite.