Mosquitos don't really make up a large portion of bat diets. That myth came from a study years back when scientists were trying to figure out how bats located prey not what prey did bats target

They study involved releasing a bat into a room filled solely with mosquitos, and it ate a lot of them, but that's because it was easy to do since it was a room loaded with mosquitos, and it was the only option for food that the bat had.

The media ran with it screaming "bats can eat a hundred mosquitos an hour!" Because it made a catchy headline moreso than the actual study results.

Bats make up less than 3% of a bats diet, depending on the species it can be higher though.

Bats typically prefer to eat larger insects such as moths, since it's more calories for the effort and they are slower and easier to find than mosquitos.