Although both Mosquitoes and Flies are both very annoying insects that I wish would go away or at least leave me and everyone else alone.
The Mosquitoes and Flies are very important to the earth and the earth would likely not fare well without them.
As for Mosquitoes and the Mosquitoes larvae are very important in aquatic ecology and provide food for fish and without the mosquitoes the fish would likely not survive unless they could eat something else.
Game fish and raptorial birds also feed on mosquitoes and mosquito larvae so they would not do well without them.
As for flies they are beneficial in getting rid of decaying matter such as animals, trash and other food from the planet.
Flies that lay the maggots help to get rid of waste such as poop, other food trash and even dead animals so without flies and maggots and other insects the earth could likely survive but it would not do well without them.