What Do Dragonflies Eat? How Nymphs and Adults Hunt

What do adult dragonflies eat?

Adult dragonflies hunt live, flying prey. Typical items include:

• Midges, gnats and mosquitoes
• House flies, horseflies and other flies
• Mayflies and caddisflies emerging from water
• Moths and small butterflies
• Flying ants and termites during their mating swarms
• Bees, wasps and beetles
• Other dragonflies and damselflies, including their own species

What a dragonfly eats depends mostly on its size. Small species catch tiny midges and gnats, while big darners such as the common green darner take larger prey such as butterflies and smaller dragonflies. Dragonflies are opportunists: they catch whatever suitable insects are flying near them, so their diet changes with the place and season.

Dragonflies also gather wherever prey is abundant. Swarms of feeding dragonflies often appear over fields when flying ants or termites emerge, or along woodland edges in the evening when midges are active.

How do dragonflies catch prey in flight?

Adult dragonflies are among the most efficient predators in the animal world. In a study of spangled skimmers (Libellula cyanea) hunting fruit flies in a large outdoor enclosure, the dragonflies caught up to about 95% of the prey they chased, and success was highest when prey was plentiful.

Several adaptations make this possible:

• Huge eyes. Each compound eye has thousands of tiny facets, more than 20,000 in some large species, giving almost all-round vision and excellent motion detection.
• Interception. Instead of chasing prey from behind, a hunting dragonfly steers so that it meets the insect where it is going to be, a little like a fielder running to catch a ball.
• Agile flight. Dragonflies move each of their four wings independently. They can hover, fly backward and turn sharply, and have been measured accelerating at several times the force of gravity during pursuits.
• A basket of legs. The spiny legs are held forward like a basket and close around the prey in mid-air. Dragonflies rarely use their legs for walking.

Once caught, the prey is bitten with strong, toothed mandibles. Small insects are eaten in flight, while large prey is usually carried to a perch, where the dragonfly removes wings and other hard parts and eats the rest, often head first.

Fliers and perchers: two hunting styles

Dragonflies hunt in two main ways.

Fliers, such as darners and emperors, patrol continuously for long periods, cruising over water, meadows or treetops and snapping up insects as they go. They are the dragonflies you see flying back and forth without landing.

Perchers, such as skimmers, darters, meadowhawks and pondhawks, sit on a stem, twig or rock with a good view. When an insect flies past, they dart out, grab it and often return to the same perch to eat. The meadowhawk in the photo above is a typical percher.

What do dragonfly nymphs eat?

Dragonfly nymphs, also called naiads, live underwater for months or years and are fierce predators of small aquatic animals. Their prey includes:

• Mosquito larvae and other fly larvae
• Mayfly nymphs and other water insects
• Water fleas and other small crustaceans
• Worms and small snails
• Tadpoles and small fish, for the larger nymphs
• Other dragonfly and damselfly nymphs

Nymphs catch prey with a unique tool called the mask. It is a greatly enlarged, hinged lower lip (labium) folded under the head, armed with hooks or spines at the tip. When prey comes within range, the nymph shoots the mask forward in a fraction of a second, driven by pressure from muscles in its abdomen, grabs the prey and pulls it back to the jaws.

Most nymphs are ambush hunters. Some lurk among water plants, others sprawl on the bottom or bury themselves in mud and sand with only their eyes and the tip of the abdomen showing. Large Anax nymphs have even been seen lunging out of the water to seize small frogs.

Do dragonflies control mosquitoes?

Dragonflies are often nicknamed mosquito hawks, and both adults and nymphs do eat mosquitoes. Popular claims that a single dragonfly eats hundreds of mosquitoes a day are not based on solid data, though. Mosquitoes are only part of a varied diet, and dragonflies hunt mostly in the daytime, while many mosquitoes are most active at dusk and night.

Even so, dragonflies are valuable natural predators of flying insects around ponds, gardens and wetlands. A healthy population of dragonflies is also a sign of clean, plant-rich water. They pose no threat to people, as explained in do dragonflies bite or sting?

Dragonflies as food for other animals

Dragonflies are also an important food for other animals. Swallows, martins, kestrels, hobbies, bee-eaters and flycatchers catch adults in the air, and frogs, spiders and robber flies take them near the ground. The American bullfrog is one of many frogs that snap up dragonflies at the water’s edge. Fish, water birds, diving beetles and other nymphs eat large numbers of dragonfly nymphs.