A mosquito (Ochlerotatus notoscriptus shown) feeding on a human arm. Mosquitoes have mouthparts that are adapted for piercing the skin of plants and animals. While males typically feed on nectar and plant juices, the female needs to obtain nutrients from a "blood meal" before she can produce eggs. In some of the 3,500 species of mosquito, the females feed on humans, and are therefore vectors for a number of infectious diseases.Photo: JJ Harrison