Female mosquito (Aedes sp.) feeding on human blood. The mosquito feeds by piercing its victim's skin with its proboscis (tube-shaped mouthpiece) and drawing blood through it. Only female mosquitoes feed on blood, which they require to produce eggs. This is the point at which pathogens are transmitted. Aedes sp. mosquitoes are vectors for pathogens such as West Nile virus, yellow fever virus, and the dengue virus.