Mosquitoes are relatively small insects, measuring an average of just more than 6 mm long and weighing about 2.5 milligrams. They're divided into three basic parts: the head, thorax and abdomen.
The head is crammed with sensory equipment that help the mosquitoes find and feed on people and animals.
They have two large compound eyes covered with tiny lenses called ommatidia that are capable of detecting even slight movement. On the top of their heads, they also have ocelli, simple photosensitive eyes detect variations in light.
Their antennae, long feathery organs, jut forward from their heads and contain sensitive receptors that detect carbon dioxide in human breath from distances of more than 100 feet. The maxillary palp between the antennae pick up the odor of ocentol and other chemicals released in human sweat.
Right in the middle, also between the antennae, is the proboscis, a long serrated mouthpart used to pierce the skin and suck out blood. The proboscis holds two tubes, one that injects saliva containing an anti-coagulant and mild painkiller, and a second that actually draws the blood.
The thorax, or what you might think of as the torso, is connected to the head. A pair of wings and a pair of halteres, small wing-like organs used for steering, sprout from the thorax. The legs also come out of the thorax, six in all, with tiny claws at the end of each to help the mosquitoes stay attached to surfaces.
The abdomen hangs from the thorax and serves as the mosquitoes' stomach and lungs.
Small openings called spiracles line both sides of the abdomen, allowing the mosquitoes to draw in air. The abdomen holds the blood that female mosquitoes take in, and a nerve in the abdomen signals when it is full. A female's eggs are also stored in the abdomen.
Scientists use small differences in the shape and coloring of the abdomen, as well as in the length of the maxillary palp and wings, to identify the various species of mosquito.