Although mosquitoes are annoying and harmful to humans when they bite us.
The mosquitoes are an important part of the environment.
Mosquitoes are very important to the life of aquatic things such as fish.
Those fish feed on the mosquitoes and larvae so the mosquitoes are an important food for the fish but even fish could likely find some other food source if mosquitoes would go extinct.
Mosquitoes are also very important and nutritious meals for birds, bats, and spiders.
But even then although they are important for them I'm sure that those animals would also find something else to eat that is more filling to them.