Have you noticed the dragonflies lately? Swooping over your front yard? Dodging the cars in the Politics and Prose parking lot? Patrolling in a loop-the-loop over your garden?
Where’s the water? Dragonflies always live near water, right? Actually, they will use any large open space to search for mosquitoes, gnats and other tiny insects. They need water to breed, and the young live there, but when they emerge they just go where the food is.
This summer I am seeing more than usual, probably because of the wet weather, and I am not the only one. Dragonflies don’t bite or sting, so take a good look and enjoy their colors and their acrobatics.
This photo of an eastern pondhawk shows how the dragonfly body is put together. You can see the green head, with eyes so big they meet in the middle. The head is attached to the blue thorax, a short sturdy organ with four wings attached. The blue abdomen stretches out almost like a tail. The wings of this dragonfly have no pattern except a small black line (“stigma”) at the upper tip of each one.
You are also likely to see damselflies, a close relative of the dragonflies. They are smaller, look more fragile, and have smaller heads and eyes. They rest with their wings folded over their backs, while dragonflies rest with wings spread out away from the body. This is a good way to tell them apart.
Dragonflies make good neighbors
Dragonflies are good to have around. They devour small insects – gnats, midges, flies, mosquitoes, even aerial plankton we can’t see. I feel lucky when a group flies over my back lawn, they are better than a mosquito zapper. Their larvae are top predators also.
Some dragonflies are known as “fliers,” hunting on the wing and staying aloft for hours. I often see them swooping over grassy areas at the community gardens on Sedgwick Street and sometimes, they’re enjoying the insect fare in the yard. The green darner is a strong flier you are likely to run across.
Others are “perchers,” sitting on a twig or blade of grass, waiting until an insect comes along, then darting out to get it. On the Linnean Avenue side of our Broad Branch stream restoration, there is a little pond where several perchers hang out. Recently there were two blue dashers working the mill-race at Peirce Mill.
How do they catch flying insects?
Experts say that dragonflies can fly up to 25 miles per hour, although 10 mph is the usual cruising speed.
How do flying dragonflies get prey that is also in the air? Their large eyes are able to see the prey from a distance and calculate where it will be when they intercept it. They have stereoscopic compound eyes with 30,000 facets, each of which is a light-sensing organ. That’s why their eyes are so big, taking up most of the head.
Their other asset is the fact that they can use each pair of wings independently. This makes it possible for them to glide, hover, speed up, turn on a dime, swerve left or right, fly backward. The wings are powered by strong muscles in the thorax, and this makes it possible for the fliers to keep hunting without rest.
The mating game
Dragonflies mate in tandem, a position which looks pretty uncomfortable to me. When a female comes into a male’s territory, he grabs her between the eyes, and she curls up and around so they form a “copulation wheel.” He transfers a packet of sperm to her. They may fly around together in the tandem position for several hours, because he does not want other males to get to her.
The female deposits the eggs at the edge of a pond or quiet water, often on leaves or in the mud. In some species she simply flies over the water, dropping the eggs in one by one.
An aquatic youth
The egg sinks to the bottom and begins the next stage. Dragonfly larvae spend growing stages in the mud or bottom of the pond. Different species will be found in streams, ponds, bogs, lakes, or springs.
They hatch from the egg in a week to several months, and some overwinter to hatch the next spring.
They are voracious eaters – a predator we can admire. They eat the larvae of insects like mosquitoes and mayflies, and even tackle small tadpoles and little fish.
As they grow, they molt – 10 to 20 times. For its final molt, the nymph leaves the water and climbs up a stem or twig. Its exoskeleton cracks, the wings come out, and the young dragonfly emerges.
Where to see them
When I talk to friends, I find that they are seeing dragonflies unexpectedly everywhere – yards, parks, playgrounds, even swimming pools. I find Rock Creek Park and the Peirce Mill area good, and I scout any swampy place, meadow or stretch of grass I pass.
The Audubon Naturalist Society (Chevy Chase, Maryland, 301-652-9188) offers occasional walks and classes. Further afield, try Dyke Marsh in Virginia or Kenilworth Aquatic Gardens (1550 Anacostia Avenue NE, DC 20019).
I would love to hear from readers. Where have you spotted dragonflies? What have you seen?
As much as I admire dragonflies, I am no expert. My sources include Wikipedia.org and the Beginner’s Guide to Dragonflies by Donald and Lillian Stokes ($9-10), which I think is the best and easiest guide for beginners to buy.