Two-foot long dragonfly seen in Rockford?
By Rod Myers
By Rod Myers
Thousands have seen a two-foot long dragonfly in Rockford; however, the dragonfly, Meganeura monyi, is a plastic replica at the Burpee Natural History Museum on North Main Street. The living version of this highly predacious dragonfly has been extinct for millions of years.
Though much smaller than two feet, the dragonflies that live today are awesome predators.
Dragonfly species number about 3,000 in the world. There is much variety in size and shape amongst the worlds species; yet, all have a common habit of being predacious. There are no dragonfly vegetarians. With their mastery of flight and huge compound eyes, they are highly adapted as predators. Inside their numerous compound eyes are thousands of simple eyes. Dragonflies can see all the colors plus ultraviolet and polarized light. They can detect the flickering of light at 80 flicks per second, which is twice what we humans can detect. They use polarized light to navigate and ultraviolet light to detect the horizontally polarized reflection water gives, making it easier to find water. Rapid light-flickering detection enables them to see the effects of rapid wing beats by other insects, a/k/a their food.
Dragonflies eat other insects, some nearly as big as themselves. A few species eat dragonflies of other species, but most prey is smaller.
If you are an insect, and youre not obscure or well camouflaged, a dragonfly in your vicinity will see you. Ive always imagined that being watched by a dragonfly is like being watched by a store with 100,000 observation bubbles on the ceiling.
Dragonflies have three methods of hunting prey. The first mode, if compared to that of a bird, is the swallow mode. Like the swallow, it hunts in flight for insects in flight. This style is common among the larger long-bodied species. Many feed in swarms, being attracted to larger swarms of small insects or what are called aerial plankton. Often, the prey is too small for us to see and is eaten on the wing. Swarming is not the only way to eat in the swallow mode; some travel alone for great distances, eating morsels here and there.
The second method is the flycatcher mode. The dragonfly sits on a perch watching for flying prey, then leaves the perch to attempt catching it. Research has shown that dragonflies using the perch method aim for the place where the prey is going to be when their flights intersect, demonstrating a very sophisticated sensory system. Skimmers and clubtail species use the flycatcher mode most often.
The third method is the kinglet mode, which is used least often. It involves flying slowly through vegetation and picking the prey from the substrate.
For the most part, dragonflies eat small insects so they can eat while flying. This summer, though, I did see a dragonfly carrying a large bumblebee. I have heard of dragonflies chasing hummingbirds, but that was probably for sport or to get the bird out of its territory. One thing, though, is most definite; dragonflies are the most skillful aerial predators in the world.
Rod Myers is a local resident with an interest in nature and the environment. He is a member of the Rockford Amateur Astronomers Club, the Sinnissippi Audubon Society, Wild Ones Natural Landscapers and the Planetary Society.