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Thursday, August 9, 2018

Nicole’s bug of the week – Dragonflies vs. Damselflies


Nicole’s bug of the week – Dragonflies vs. Damselflies
This week’s Bug of the Week article is a two-for-one deal. It will cover both dragonflies and damselflies and how to tell the two apart. Both dragonflies and damselflies are of the order Odonata and are therefore referred to as odonates. Due to this they have many similarities, but don’t worry; they do have a few obvious differences. As dragonfly spotting has become an increasingly popular hobby, much like bird watching, it could be a handy skill to be able to tell them apart from their close cousins.
As members of the same order, dragonflies and damselflies have much the same life cycle. The adults will lay their eggs at, on, or near bodies of water such as ponds, lakes, or rivers, and the naiads (naiads are nymphs or pupae which are water dwellers) will hatch out in one to two weeks. The naiads of the two odonates look fairly different, but keep much the same diet, feeding on mosquito larva, other small aquatic bugs, and even small tadpoles. As for looks, both types of naiad have big heads with big eyes, long bodies, and six legs. Damselfly naiads, however, will be much more slender and will have three flexible, leaf-life gills at the end of their tails. Dragonfly naiads will be wider with hard pointed tails and no external gills (they have internal gills that they can also use to shoot themselves through the water!)
Dragonfly in flight
 
 
Damselfly at rest

 
After two to three weeks as naiads, they will form cocoons and emerge in one to three weeks as adults. As adults, the easiest way to tell them apart from a distance is to wait for them to land and then observe the positon of their wings. If it holds its wings flat out, horizontal to the ground, it’s a dragonfly; if it holds its wing together roof-like over its back, it’s a damselfly. If you can get closer to one, the next easiest method to use is to identify the shape of its body. Where a damselfly’s body will be about the same thickness all the way down, a dragonfly’s abdomen will be noticeably thicker than its ‘tail’. One of the favorite foods of both odonates is mosquitos, and they help keep the population down, protecting you from mosquito-borne diseases! They can also eat the eggs of caterpillars and other pests that would otherwise chew up your garden, making them very sought after backyard guests.
So maybe the next time you’re swimming at the lake or enjoying a picnic next to a pond and you see one of these guys buzzing around, you’ll be a little more knowledgeable about them and might even be able to wow your friends with your identification skills! Even if you don’t get too into dragonfly spotting, they’ll still be around keeping you (and your garden) safe.

Borror, Donald J., Triplehorn, Charles A., Jonson, Norman F. “An Introduction to the Study of Insects.” Sanders College Publishing, 1989, pg. 194
Metcalf, C. L., Flint W. P. “Destructive and Useful Insects.” Theirs Habits and Control, R. L. Metcalf, McGraw Hill Book Company, 1962, pg. 205
Borror, Donald J., White, Richard E. “Insects.” Peterson Field Guides, R. T. Peterson, Houghton Mifflin Company, 1970, pg. 80

Thanks Nicole,
Blayne

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