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Why Do We Only See Dragonflies In The Summer?



SCOTT SIMON, HOST:

A summer image now – dragonflies skimming over a lake, lighting on the surface for a moment then rolling off again. That’s all in a day’s work for Dr. Jessica Ware. She studies dragonflies at Rutgers University. She’s going to tell us about them for our summer series, What’s Bugging You? She’s at the studios of WBGO in Newark. Thanks so much for being with us.

JESSICA WARE: Thanks for having me.

SIMON: Why do we only see dragonflies in the summer?

WARE: Well, I think it depends on where you’re looking. They’re really colorful and obvious near the water in the summer. That’s the adult stage of the dragonfly. But all dragonflies and damselflies have an immature stage which inhabits freshwater. The females lay eggs, the eggs develop into nymphs or larvae and the larvae live over the fall, winter and spring in the water.

So if you were to go out in the fall, winter or spring, you can still find dragonflies. You’ll just find something that looks very different (laughter). Usually the nymphs are kind of small and stubby. They have big jaws for catching tadpoles and minnows and other aquatic insects, and they’re usually dark brown in color.

SIMON: And I’m told their mating can be pretty fraught, and I know, speaking on behalf of our species, it always is. But how so with dragonflies?

WARE: Definitely, I would say, it’s dramatic is one way to describe it. Some males are involved in kind of dramatic territorial fights near the water. Calopterygid damselflies, which are the ebony jewelwings, they have kind of green metallic bodies with black wings. They’re very striking. Those males actually will kind of do dancing competitions, if you will, where they, you know, will fly for extended periods of time with really kind of acrobatic maneuvers. And then eventually one male will use up all of its fat storers and will fall into the water dead.

SIMON: Without having mated?

WARE: Without having mated. And the other male…

SIMON: Oh, what a doofus.

WARE: (Laughter) Well, it gets worse. The other male will be able to mate with the female. But meanwhile, while those two males are fighting, there are other males, which we call sneaky males, that will just go and mate with females (laughter) that are hanging out at the water…

SIMON: My gosh.

WARE: …Waiting for the dance contest to finish.

SIMON: I’m exhausted. You know…

WARE: (Laughter) I think they are, too, after it.

SIMON: Moving on just a bit, how fast can they fly?

WARE: Oh, well it depends on the species. So some aeshnids – aesnidae is a family of dragonflies called the darners – and they can fly very fast, you know, 30 kilometers – 30 miles an hour, rather. There are some dragonflies and damselflies that fly very slowly. And there are some dragonflies that, you know, fly very long distances and migrate, you know, around the globe.

SIMON: There are some that will lift off from a pond in New Jersey and fly to where?

WARE: Well, I mean, we have done some work in my lab on a genus called Pantala, and there’s some evidence to suggest that they fly basically around the entire globe. The genetic evidence suggests that things that were collected in Japan were really closely related to things that were collected in Guyana, South America, in New Jersey. So it seems like they can fly quite long distances.

SIMON: Dr. Ware, may I ask, where did you grow up?

WARE: I grew up in Canada, and I was raised mostly by my grandparents who had a house up in Northern Ontario. And we spent most of our time up on a big lake that was full of dragonflies, which is partly why I got excited about them.

SIMON: Yeah, I was almost going to say that’s how you got the bug, but that’s how you – I know, sorry. You must hear that all the time.

WARE: (Laughter) It’s true. I mean, whether you’re an urban dweller or whether you live in a rural setting, dragonflies are ubiquitous. I would say that they’re a common feature in many cultural stories. My grandmother used to say if you fell asleep on the dock, they’d come and sew your lips shut (laughter), which is why aeshnids are called darners. They’re called darning needles. And other cultures have very positive connotations. And in Japan, one of the names, so they say, of one of the islands is actually Island of Dragonflies.

SIMON: Dr. Jessica Ware, who studies dragonflies at Rutgers, thanks so much for being with us.

WARE: Thank you for having me.

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Article source: http://www.npr.org/2016/08/27/491613567/why-do-we-only-see-dragonflies-in-the-summer?utm_medium=RSS&utm_campaign=science