The answer to 'what causes mosquito' is mosquitoes are attracted to humans and other warm-blooded animals by the carbon dioxide we exhale, as well as the heat and certain chemicals on our skin. Mosquitoes use these cues to locate potential hosts to feed on. They are also drawn to standing water, which is where they lay their eggs.
Mosquitoes have a complex life cycle that includes four stages: egg, larva, pupa, and adult. The adult female mosquitoes are the ones that bite and feed on blood, which they need to develop their eggs. After mating, the female mosquitoes seek out standing water to lay their eggs, starting the cycle over again.