As adults, dragonflies eat other insects and can consume hundreds of mosquitoes in one day! typically eat mosquitoes and other small insects. They are valued as predators, since they help control populations of harmful insects. Dragonflies are usually found around lakes, ponds, streams and wetlands because their larvae, known as "nymphs", are aquatic. Adult dragonflies do not bite or sting humans, though nymphs are capable of delivering a painful but harmless bite.