Why Do Mosquitoes Suck Blood?

Answer:

Mosquitoes’ reputation for peskiness is only half deserved, for only the females of the blood-sucking species suck blood. The males live on plant juices and nectar. A mosquito does not have biting jaws. Instead, its mouthparts are modified for piercing and sucking. As the mosquito penetrates the victim’s skin with its needlelike proboscis, it injects saliva laden with a substance that keeps blood from clotting. It is a reaction to this substance that causes the subsequent itching and swelling of a mosquito bite.

Mosquitoes belong to the fly clan, and numerous other species — including black flies, horseflies, deerflies, and greenhead flies — share the bloodsucking propensity. In these insects, too, only the adult females suck blood; males live on nectar and pollen. Both male and female African tsetse flies, carriers of deadly sleeping sickness, feed on blood.