Friday, June 29, 2012

Dragons in the Sky

eastern pondhawk. photo by Jo Smith

Dragonflies zip above my hayfield, stitching together pieces of the sky. They’re busy, hunting down gnats and mosquitoes, but every now and then one stops for a moment, perching on a seedy head of grass or a flower.

Hunting gnats is tough – how does one see those tiny pesky things while flying 20 to 38 miles an hour? The key for dragonflies is their compound eyes. Each eye is made up of as many as 30,000 six-sided facets. Those eyes can detect motion as far as 65 feet away. Watch out mosquitoes!

The other neat thing about dragonflies is their wings. Dragonflies can fly backwards, hover, and even loop-the-loop. Like bees and butterflies, dragonflies have four wings. But unlike bees and butterflies, dragonflies can move their front wings independent of their hind wings. It’s like four-wheel drive, but with wings.

A few years ago some scientists tethered dragonflies in a wind tunnel and took photos of their wings in flight. They discovered that dragonflies twist their wings on the down stroke, creating an airflow that generates enough lift to keep 15 – 20 times their weight in flight. Wouldn’t it be cool if aircraft could do that? You can bet some engineers are already on that.

Spend some time watching dragonflies this summer. You can help scientists learn more by becoming a "citizen scientist" for Dragonfly Pond Watch.

It's STEM Friday! Check out books and resources here.

1 comment:

  1. I love dragonflies! And I love the Asian and Native American symbolism around dragonflies too:
    • prosperity
    • good luck
    • strength
    • peace
    • harmony
    • purity

    Thanks for an interesting article.