27 May 2011

Dragonflies: Vision equals speed

By Marie Powell

The thrum of dragonfly wings is the most welcome sign of summer for me. Dragonflies can fly as fast as a car drives on city streets. They can hover like helicopters in the air. They’re known as great fliers, and one of the advantages they have in the air comes from their sight.

Dragonflies have two large compound eyes, and three ocelli or simple eyes. Each compound eye has about 30,000 tiny, six-sided lenses or facets, to help them see more clearly. With thousands of different species, there are likely variations in the way they see. Scientists speculate that most dragonflies can see colour better than humans. Dragonflies also see polarized light and ultraviolet light.

Dragonfly eyesight becomes a big advantage to them in flight. They can see in front and behind them with their compound eyes. They see what’s around them quickly and accurately. Another big advantage is the way they are able to see movement. As hunters of other speedy insects, that’s what they need to survive.

I love finding out about dragonflies. That's one reason why I wrote a book about them: Dragonflies are Amazing! (Scholastic Canada, 2007). I still enjoy finding out about dragonflies and dragonfly eyes. Here are a few online links that I like:

Australian National University: Australians seem to be the experts on dragonflies, and they are looking at its eye in a study of new flying vehicles for people!

Living the Scientific Life blog: “30,000 Facets Give Dragonflies a Different Perspective: The Big Compound Eye in the Sky.” This blog article has great pictures and interviews with scientists who are also dragonfly experts. (But please don’t follow the advice to catch dragonflies in nets: it could damage their wings. Try standing still to let them land on you instead. That way you can examine each other!)

Dragonflies of Manitoba: This website has amazing animated pictures, as well as video clips. (Note: Plug-ins are required for videos, but information is also available without videos.)

There are lots of online links to explore for more info on insects. Happy hunting!

Marie Powell is the author of Dragonflies are Amazing! (Scholastic Canada, Grade Two Guided Reading, 2007).

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