August 21, 2013

Dragonfly sight unseen

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A meadowhawk dragonfly, of the skimmer family.

Staff photo by Dana Wilde

Fourth, dragonflies have a spot on their eyes called a fovea, which is a dense cluster of ommotidia cells that sharpens the images of what they see, especially the blue and ultraviolet colors. Humans, who see very well as creature eyesight goes, also have a fovea, but our eyes are not facet-based, so the fovea’s effect is different for us.

So what do dragonflies see? The flicker effect gives them a keen sense of motion so they can locate and grab flying insects with startling precision. Their polarotaxic ability reveals to them a sky that to us is just a glare, but to them is a bright background that they can navigate by. The colors they see that we don’t are reflecting off flowers, leaves and water; two black-eyed susans that look exactly the same to us have varied color patterns to the dragonfly. Their thousands of facets pick up not just what’s in front of them, but also what’s all around them within a yard or so.

Their little odonate minds are glimpsing moment-by-moment snapshots of a world that we are right in the middle of, but don’t see. So when they were not showing up in the yard this June, I admit I felt a little lost. Was blind, as it were, but now thankfully can see them.

Dana Wilde lives in Troy. His writings on the Maine woods are collected in “The Other End of the Driveway,” available from Booklocker.com and online book sellers. Backyard Naturalist appears the second and fourth Thursdays each month. You can contact him at naturalist@dwildepress.net.

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