As adults, dragonflies feed on other live insects. They aren't picky eaters. They'll eat any insect they can catch, including other dragonflies. Midges and mosquitoes make up the bulk of their diet, but dragonflies will also prey on flies, bees, beetles, moths, butterflies, and other flying insects. The larger the dragonfly, the larger the prey insect it can consume. A dragonfly will eat roughly 15% of its own body weight in prey each day, and larger species can easily consume much more than that.
Most dragonflies capture their prey in flight, plucking live insects right out of the air. They're well equipped for pursuing and capturing flying prey. Dragonflies can accelerate in an instant, turn on a dime, hover in place, and even fly backwards. By forming a basket of sorts with its legs, a dragonfly can overtake a fly or bee and simply scoop it up and pop it into its mouth, without stopping. Some, like darners and spreadwings, will just open their mouths and swallow whatever they catch as they fly. Other dragonflies use a strategy called gleaning, preferring to hover over vegetation and snatch insects perched on plant leaves or stems. Immature dragonfly adults, which often hunt in forested environments, will grab and eat caterpillars suspended from the trees by silken threads.
Dragonfly nymphs, which live in water, also feed on live prey. A nymph will lie in wait, most often on aquatic vegetation. When prey moves within reach, it unfurls its labium and thrusts it forward in an instant, grabbing the unsuspecting critter with a pair of palpi. Larger nymphs can capture and eat tadpoles or even small fish.
- Dragonflies, by Cynthia Berger, 2004.
- Borror and DeLong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson, 2005.
- Encyclopedia of Insects, 2nd Edition, by Vincent H. Resh and Ring T. Carde, 2009