system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Lets pretend i killed every single mosquito and fly in the world. would i cause some sort of disaster?
gpt
Mosquitos and flies are 'bottom of the food chain'.  Yes they bite us and annoy us.

But mosquito larvae are amazing fish-food.  They take tiny bits of algae, that are useless to most aquatic organisms, eat it, and convert it into a nice high protein snack for fish/fish-fry (Baby fish).

MANY frogs rely on fly larvae to survive.

There are also many species of flowers that rely on flies to survive.  Most famous is the Corpse Flower (It smells like death/decay and thus attracts flies for pollination)

Mosquitos and flies are just part of the food chain.  To make too big a dent in them would result in food shortages for many other organisms.  
Perhaps it helps to think that "The best use for flies and mosquitos is their babies.  Their babies are excellent food for many organisms"