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June 1, 2020

5/22/2020 7:27:00 AM
Everything I ever wanted to know about dragonflies, but was afraid to ask
Beckie Gaskill
Outdoors Writer

As many who read the Outdoors section of this newspaper are aware, the Lakes and Rivers Convention, originally slated to take place at the Holiday Inn and Conference Center in Stevens Point, was turned into an online event. It was still very widely attended, and there were so many great sessions that it was hard to decide what to attend.

But, we are all very lucky in one way. While we were unable to get together and network as we normally would at a Lakes Convention, one of the coolest parts is every session we could have attended is now available online. Yesterday I grabbed a cup of coffee and sat down to view Emily Heald's presentation on dragonflies. Heald is the water program coordinator at North Lakeland Discovery Center, as many already know. I thought: This should be cool. Dragonflies are pretty and kind of cool.

Holy smokes. I had no idea how cool dragonflies were. Heald presented some interesting facts such as the fasted recorded speed of a dragonfly is 60 miles per hour. Yes, 60. Crazy to think about. Aldo fossil records put dragonflies on the Earth up to 350 million years ago. Like many animals, they were a bit different back then, apparently. Can anyone imagine a dragonfly three feet long? Another crazy fact. They were that big, according to fossils.

Today, there are over 5,000 species of dragonflies in the world, and 110 in Wisconsin.

Heald took us through the complete life cycle of the dragonfly in her presentation, which I would really recommend to anyone who is even slightly interested in the subject, or in learning something new in general.

Dragonflies are anthropods. Heald went through the kingdom, phylum, class and order (odanata) of dragonflies. Then she explained the life cycle, right from egg laying. Dragonflies, she said, lay their eggs in a number of ways including scattering, where they female dragonfly simply flies over the water dropping her eggs. Eggs of some species may also be found as a sticky string attached to plant matter. Other kinds of dragonflies insert their eggs either into a plant stem or into sediment. Insertion into a plant stem is achieved through the dragonfly slicing into the plant with its tail and laying the eggs inside the plant, which I thought was pretty interesting.

Once the dragonflies hatch, they are in the nymph stage, where they spend 90% of their lives. The stage can last from several months to several years. This is another fact I guess I never thought about. We see dragonflies and just assume it was kind of a short process to get to that stage. Not the case, apparently. Dragonfly nymphs can undergo up to 15 molts during their nymph stage.

Dragonflies in general, at any stage, are voracious and adept predators. They will eat anything as nymphs, including other nymphs.

Their mouth parts, or labium, can extend up to a third or the length of their body. Heald made the comparison to herself, at just over five feet tall, and what it would look like if she had mouth parts that could extend that far. This made me chuckle, but it also makes a person think about what kind of reach this would give the dragonfly nymph. Again, a crazy little fact. As they say, now that is something that you know. You are welcome.

While they are voracious predators, these nymphs are also important in the food web as a food source. They are eaten by fish, birds, other insects, and, as I said, even other nymphs. So they are pretty important all around.

The nymphs move to land for their final molt. As we can imagine, this is the most vulnerable stage for the dragonfly. In fact, Heald said they have approximately a 90% mortality rate at this point. They complete this final molt overnight, which gives them a bit better chance of survival, but 90% is still high. She showed a time lapse of a dragonfly emerging, with its head and back first, waiting until its legs hardened. From there, it fills its wings with fluid until they unfurl. There are videos of this on YouTube that are really worth a view for those interested. It is a neat process. Once the wings unfurl, the dragonfly pulls the water back into itself and the wings dry out. During this process, the dragonfly, of course, has no defenses. The entire process can take 45 minutes to an hour.

Those that survive the process can be seen as the dragonflies we know and love. When they first emerge, their wings are shiny and their eyes dull. Their bodies also look somewhat soft.

Heald said dragonflies cannot smell, hear, or vocalize, something else I never thought about. They can see very well, however. In fact, their eyes have 30,000 lenses. They can see almost 360 degrees and can see ultraviolet and polarized light. They can see so well, she said, that they can discern individual wing beats of their prey, to determine how fast the prey is moving and in what direction.

Dragonflies themselves can fly in any direction, as most of us have experienced. They can fly backward, forward, up, down, side to side and even hover in one spot.

Another interesting fact Heald mentioned in her presentation was how a dragonfly's wings are attached.

With most arthropods, the wings are attache to the exoskeleton. In the case of dragonflies, the wings are attached directly to the thorax, or body, of the animal. This means the wing beats of the dragonfly are much stronger than the typical arthropod. Also, each wing can move individually, which gives the dragonfly its mobility.

She said airplane companies have even studied the dragonfly to get a better idea of its aerodynamics.

The legs of the dragonfly are made specifically for eating, it seems. While the mouth parts extend to help the dragonfly pull in its prey, they can use their legs, which are very hairy, to scoop in prey as well. Heald likened their legs to little baskets and also showed a video of this in her presentation.

These little guys (and girls) have an 80-95% predation success rate. That means 80-95% of the time a dragonfly gets the idea to eat something, it is successful. Peregrine falcons, she said, which are thought to be great predators, only have a 47% predation success rate. When we look at the fact that dragonflies need to eat 10-15% of their body weight every day, I suppose it is a good thing that they are such successful predators.

There was far too much information in Heald's presentation to include here, but I would encourage those interested to seek it out on the UW-Extension Lakes website under the Convention 2020 archives. One last thing: There is an app for that. Most people know I am all about outdoor apps, and this is a fun one Heald presented that I am looking forward to using - Dragonfly ID. With over 110 species of dragonflies in Wisconsin, and over twice that many "looks" of different life stages and sexes of the dragonflies, identification can be difficult at best. This app allows the outdoors person easy access to at least a fairly good guess as to what they are seeing. I look forward to using it this summer.

Beckie Gaskill may be reached at bgaskill@lakelandtimes.com or outdoors@lakelandtimes.com.





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