General prey for a dragonfly would include all of the most pesky insects, staying within the range of mosquitoes, flies, bees, and wasps. However it is known that a hungry dragonfly will take a butterfly as lunch.
A dragonfly has four wings and very evolved eyes, allowing for maximum agility and visual analysis. When attacking a dragonfly will come from behind and below its target, literally ambushing the prey. This in combination with their protruding prehensile labium make the dragonfly an insect eating machine!
This appetite qualifies them as a positive impact on the environment and ecosystem, acting as an insect population control measure.