Dragonflies have been flying around my life a lot lately. I've had many conversations about them and a few days ago a struggling dragonfly came to land on my nephew. He's a curious one (my nephew, not sure about the dragonfly) so it was very exciting. I was a little sad because it did seem as if the dragonfly was on it's last leg, so I was trying to figure out how to make it as comfortable and safe as possible (while still sharing in the joy of a pretty bug landing for our viewing pleasure). It's mouth was moving so of course I start thinking about food, I then realized I had no idea what dragonflies eat... Another perfect question for the Daily Doodle.
Dragonflies were some of the first winged insects to evolve, some 300 million years ago. Modern dragonflies have wingspans of only two to five inches, but fossil dragonflies have been found with wingspans of up to two feet. Some scientists theorize that high oxygen levels during the Paleozoic era allowed dragonflies to grow to monster size.
There are more than 5,000 known species of dragonflies, all of which (along with damselflies) belong to the order Odonata, which means “toothed one” in Greek and refers to the dragonfly’s serrated teeth.
In their larval stage, which can last up to two years, dragonflies are aquatic and eat just about anything—tadpoles, mosquitoes, fish, other insect larvae and even each other. At the end of its larval stage, the dragonfly crawls out of the water, then its exoskeleton cracks open and releases the insect’s abdomen, which had been packed in like a telescope. Its four wings come out, and they dry and harden over the next several hours to days. Some adult dragonflies live for only a few weeks while others live up to a year. Dragonflies are expert fliers. They can fly straight up and down, hover like a helicopter and even mate mid-air. If they can’t fly, they’ll starve because they only eat prey they catch while flying. Dragonflies catch their insect prey by grabbing it with their feet. They’re so efficient in their hunting that, in one Harvard University study, the dragonflies caught 90 to 95 percent of the prey released into their enclosure.
The flight of the dragonfly is so special that it has inspired engineers who dream of making robots that fly like dragonflies. Nearly all of the dragonfly’s head is an eye, so they have incredible vision that encompasses almost every angle except directly behind them.
Dragonflies, which eat insects as adults, are a great control on the mosquito population. A single dragonfly can eat 30 to hundreds of mosquitoes per day.
Hundreds of dragonflies of different species will gather in swarms, either for feeding or migration. Little is known about this behavior, but the Dragonfly Swarm Project is collecting reports on swarms to better understand the behavior. (Report a swarm here.)
Scientists have tracked migratory dragonflies by attaching tiny transmitters to wings with a combination of eyelash adhesive and superglue. They found that green darners from New Jersey traveled only every third day and an average of 7.5 miles per day (though one dragonfly traveled 100 miles in a single day). A dragonfly called the globe skinner has the longest migration of any insect—11,000 miles back and forth across the Indian Ocean.
