COLUMN: Why are there so many dragonflies?

     This month I’ve been receiving many calls and questions on dragonfly sightings.  Everyone wants to know why there are so many dragonflies and where they have come from? The information below from 2014 is just as relevant today, in 2019. We still have much to learn about insect migrations, including the fall migration of many dragonfly species.

     Dragonflies belong to the Odonata order of insects, which includes over 5,000 species of dragonflies and damselflies worldwide.  Over 447 species can be found in the United States with 51 species recorded in Jones County, Iowa according to the Iowa Odonata survey.   It takes a little effort but when you concentrate on watching them you can see the different colors and patterns of each individual species.

     Dragonflies are typically observed near a pond, lake, wetland, or slow moving stream or river. Males of many species will have defined territories in these locations and can even be observed patrolling their area. Noticing this requires a comfy chair or boat cushion and some quiet time near the water, on your deck, or just in your backyard. You might notice the territorial male chasing away intruding males and courting receptive females. Depending on the species, female dragonflies will then lay their eggs in the water, on a plant, or in the mud along the edge of the water.

     Most dragonfly eggs will hatch during the summer, although some will overwinter in the egg stage. Larvae, called nymphs, emerge from the eggs and try to blend in with their underwater environment, where they will live and hunt for aquatic insects, larvae, small fish, and tadpoles as they grow. Nymphs can take anywhere from one to six years underwater growing and repeatedly shedding their skin. When they are ready to shed their skin the final time, they emerge from the water and attach to a stick, dock, tree, plant, or rock. Then the nymph’s skin splits open and out crawls a fully developed adult dragonfly. After a few hours of pumping up and drying its wings it will be ready for its first flight.

     Dragonflies can be observed throughout the summer, but if you are in the right place at the right time you might see one of nature’s spectacular treats – a “dragonfly swarm.” Hundreds and sometimes thousands of dragonflies, often made up of multiple species, flying together in a well-defined area make up a swarm. These foraging swarms form for the common purpose of catching and eating an abundant food source.  Here in Iowa this is usually a hatch of flying ants, an abundance of gnats, midges, and sometimes mosquitoes.

     There are a few species of dragonflies, especially the common green darner, which will migrate. Some of the swarming behavior from August through October could be from dragonflies migrating. Although with this behavior you will notice a very directional oriented flight pattern. It is interesting to note that many people observe migrating dragonflies at the same time that they notice migrating monarch butterflies, both of which seem to migrate associated with the passage of cold fronts during the fall.

     Relatively little is known about dragonfly migrations and dragonfly migration research is ongoing.  Citizen reports are especially helpful. If you are interested in learning more about Iowa’s dragonflies visit the Iowa Odonata website at http://www.iowaodes.org/ where you can find a species list by county as well as great images and detailed information on each species.

     To report migratory dragonfly sightings, visit the Migratory Dragonfly Partnership website at http://www.migratorydragonflypartnership.org and the Xerces Society for Invertebrate Conservation at   https://xerces.org/dragonfly-migration/.