“Arthropods, a group that includes insects, spiders, and crustaceans, make up roughly half of all animals on Earth, by biomass. There are, for example, an estimated 20 quadrillion ants. And because insects are superabundant and everywhere — in streams and lakes, deserts and mountaintops — they are essential parts to every ecosystem.
Scientists estimate that about 90 percent of flowering plants are pollinated by animals, most of which are insects. More than a third of our food crops depend on pollinators, including almonds, chocolate, and coffee.
Insects also make up a huge part of the diet of many animals. Nearly all terrestrial birds in North America feed their young invertebrates. “If you like birds, you should thank an insect,” Black said.
Many fish eat insects, too, including salmon, he said. “They would not make it to the ocean without feeding on insects,” Black said. “This goes all the way up the food chain. Think of grizzly bears. They eat salmon, which rely on insects. And their other main food source is berries, which are insect-pollinated. So bears almost exclusively eat a diet that comes from insects.”
Also worth mentioning: Insects, like dung beetles, clean up animal feces that might otherwise smother the ground and fill the air with a foul stench.”
https://www.vox.com/explain-it-to-me/371434/insect-apocalypse-bees-decline-loss