Thursday, June 17, 2010

Dragons and Damsels

The excess rain may cause some problems, but I’ve been enjoying having so much water in the pond. By the Fourth of July the pond is normally so shallow that the raccoons can wade into the middle and dine on any remaining tadpoles or large insects. The pond level now is more typical of what you would find in April and those insects that require a larger body of water are swarming in. The rushes are not completely inundated and provide the perfect structure for aquatic insects to use for egg laying.

The air around the pond is a constant buzz of dragonfly wings. Some species, like this Common Whitetail, have established territories and stand guard from some stationary vantage point. Common Green Darners and some others never seem to land and continually circle the pond, being chased by different individuals as they cross from one territory to another.

One of the most common dragonflies is the Blue Dasher. Several of this species can usually be found around the water garden each year, but with the pond available, they are here in amazing numbers.

Blue Dashers will often raise their abdomen until it points directly upward. Literature suggests that they point the tip of the abdomen toward the sun in order to reduce exposure and avoid overheating. I noticed some individuals exhibiting this posture in the shade. This photo was taken in late afternoon and this west facing dasher increased its exposure to the sun by assuming this posture. The temperature was about 90 degrees F, so the insects were probably warm. Maybe the up abdomen posture is a cooling strategy that works by other means than just reducing contact with the sun’s rays.

Here is a pair of Southern Spreadwing damselflies. Spreadwings are usually noticeably larger than the common damselflies and hold their wings apart when at rest. The female places her eggs above the water line and inside living plant stems. The female of this pair probed every stem they landed on, but I couldn’t tell if she was actually laying any eggs.

This damselfly is one of the bluets, and holds its wings together while at rest. These damselflies always seem so dainty and fragile. It’s hard to think of them as winged killers that spend their days munching away on mosquitoes and other small insects. I’ve watched damselfly larvae in an aquarium eat mosquito larvae as fast as they could be caught. They may be small, but they are certainly not helpless.

6 comments:

  1. while mowing in a wet area of my lawn yesterday I saw a white tail...and of course no camera...I might just mount one on the hood of the mower!! :} Oh and by the way... I don't know one dragonfly name from another.. got this name (White tail) from a blogger friend...;}. Thanks for making me a little more savy on this subject!!

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  2. What a great post, Steve! I've been watching dragons and damsels out here in CA and am just learning about them. I was especially interested in your exploration of the vertical Blue Dashers. I haven't seen that group around here yet but will keep an eye out!

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  3. grammie g - Definitely do something to keep that camera near by. When I bought my camera, I made sure I got one that fit into a neat little pouch that attaches to my belt. My camera goes with me every time I leave the house.

    Debbie - According to the range maps, Blue Dashers are fairly common in California. They're fairly active and let you get pretty close. They also keep returning to the same perch. Sometimes I get within a few feet and then just sit and watch them hunting or chasing away other insects.

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  4. My first thought at the upward pointing abdomen was some sort of territorial or mating display - as visual and territorial as dragonflies are, I expect all that color is used for something.

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  5. The dragons and damsels are just now coming out here in Atlantic Canada. Sadly, we don't seem to have Whitetails. I appreciated this informative post with such a lovely assortment pictures. I second the suggestion to never be caught without your camera! It's when you don't have it in your hands that the most amazing photo op presents itself! ~karen

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  6. I agree, Ted. It just seems so logical that the posture would have something to do with interactions with other dragonflies. In Dragonflies and Damselflies of Ohio, Glotzhober and McShaffrey attribute it to sun exposure.

    Karen - I guess with your shorter season you've got to rush to enjoy all of the summer encounters. It's a shame about the Whitetails. They're really an attractive dragon.

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