Only female mosquitoes drink blood. Males are vegetarians.
The male mosquitos are strictly vegetarian and the females drink blood for nourish their child-bearing bodies. A human Blood is full of proteins and amino acids & that makes it the perfect prenatal supplement for growing mosquito eggs. So that’s why female mosquitos drink Human’s or animal’s blood.
Male mosquitoes are harmless and will not drink blood, yet they do usually drink nectar for their nutritional needs.
In many mosquito species, the mouthparts of the females are adapted for piercing the skin of animal hosts and sucking their blood, wheres the males lack this mouthpiece. This makes it impossible for most male mosquitoes to drink the blood of other species. For a male, it would not make sense to do this either, since they do not need to lay eggs and produce offspring (other than mating with the females).