By Kathy Biggs
Dragonflies are large and often flamboyantly-colored insects, as you can see. This male Flame Skimmerâ€™s scientific name denotes how its body is saturated with color.Â What many folks donâ€™t know about dragonflies, however, is that by far the largest part of their lives is spent as nymph underwater, where they breathe through gills. Both dragonflies (Anisoptera) and damselflies (Zygoptera) belong to the scientific order Odonata, and both of these suborders go through very similar development.
A dragonfly starts its life as an egg that is laid in water, or in plant matter on the water. This female Common Whitetail is adding eggs to a floating mass of previously deposited eggs. She accomplishes this by tapping the end of her abdomen on the water. Other species might not amass such a conglomeration of eggs, laying an egg here or there, or they might make slits in vegetation and place one or two eggs in each slit.
Females can oviposit hundreds of eggs each day and usually mate several times, although each female probably retains enough sperm from just one mating to fertilize her lifetimeâ€™s supply of eggs.
In general the eggs hatch in about a week, although the weather, water temperature and other factors influence how quickly they hatch. Some eggs are even laid on the shoreline of lakes, not beginning their development until spring when winter rains have washed the eggs into the lake, or the lake level has risen to cover them.
The nymph that emerge from the eggs spend about a year growing; again, water temperature and also the abundance of food affect the growth cycle. They progress through several instars, averaging about a dozen before they are ready to begin their metamorphosis. With each instar, they shed their outer exoskeleton, exposing a new one that they inflate and grow into. I sometimes think of this phenomenon as akin to buying new clothes for children as they grow!
As you can see, dragonfly nymph look a bit like six-legged spiders!
While living under-water, dragonfly and damselfly nymph breathe through gills. Dragonfly nymph have gills located within their bodies, while Damselfly nymph have three external feathery gills at the end of their abdomen. Skimmers are a family of dragonfly; their nymph are shown in the scan above.
As the nymph molts, it grows longer and longer wing-bud covers over the abdomen. When the nymph is ready to go into its amazing metamorphosis, the wing pads over its body are about half the body length.
This nymph has just climbed out of the water and is beginning its metamorphosis. Dragonflies have what is considered an incomplete metamorphosis as they do not have a four-stage transformation, such as butterflies do. They go straight from aquatic nymph breathing through gills to flying, air-breathing adults without a cocoon, chrysalis or pupal stage.
The nymph in the photo above has already puffed itself up with air, has split its exoskeleton over the top of the thorax and has begun emerging.Â Itâ€™s head and thorax have already come out. This part of the process takes only a few minutes once the nymph has climbed out of the water and has secured itself on the plant matter. This nymph chose to emerge on Mareâ€™s Tail (Hippuris vulgaris) by attaching small claws at the end of its tarsi (feet) into the vegetation.
A dragonfly nymph is totally helpless at this stage in its life. Many predators – birds, fish, and other dragonflies – feed on emerging dragonflies. Iâ€™ve been surprised to find that even lizards and chipmunks run around my pond, looking for these delicacies. Ants attack emerging dragonflies, even our tiny â€œsugar antsâ€. They overwhelm the helpless dragonfly.
After its legs harden (generally about a half hour, depending on temperature and humidity), the nymph lunges forward and grabs hold of its exoskeleton, and then pulls the rest of its body out. At this point, it starts to puff up its body and its wing-buds (like blowing up a balloon). Notice that the newly emerged dragonfly is now about twice the size of its old exoskeleton. The old exoskeleton, which will be left behind, is now called an exuvia (x-zoo-v-ah).
Next, the emerging dragonfly begins to push a blood-like liquid through its wing buds and they enlarge, in much the same way that emerging butterflies inflate their wings. When both the wings and body are fully inflated, the dragonfly will spread its wings to dry.
Not until the wings are dry can it fly away, so it spreads them out, orienting its body towards the warming rays of the sun. Sometimes the teneral dragonfly (think of it as being â€œtenderâ€) flies just a short distance to a nearby perch to finish drying, and other times it may rise in a â€œbee-lineâ€ at a 45 degree angle, going up, up and away, letting the wind currents carry it to a distant place. But, all dragonflies leave the area of their natal water to mature. They need to harden their bodies and develop their mature coloration.
The tender, newly emerged dragonfly flies away from its birthplace to grow up a bit. It takes about a week, in general, for the dragonflyâ€™s body to harden and for the colors to develop. Newly emerged dragonflies must leave the water source they emerge from to escape predation and damage caused by mature dragonflies. If they stayed, they would engage in battle and would lose because their body would still be tender and their ability to maneuver in flight not practiced yet.
Pictured is an adult, fully mature and colored, male Cardinal Meadowhawk, the same species that emerged in the preceding images. His bright colors are the same shade as the bird species, the Cardinal. This bird, with its characteristic topknot, is named after the Catholic Cardinal who wears a pointed hat.
Once a dragonfly has emerged and become a mature, flying insect, it lives for only a few more weeks, just long enough to mate and ensure its bloodline. So, when you see one of these little shining jewels, stop and marvel at its beautiful colors and behaviors, and remember its amazing transformation from underwater nymph to magnificent flying predator.
About the author:
Kathy Biggs is the author of 2 dragonfly guides:
Common Dragonflies of California, A Beginnerâ€™s Pocket Guide
Common Dragonflies of the Southwest, A Beginnerâ€™s Pocket Guide
Each guide has a companion website:
Dragonflies (Odonata) of California
Dragonflies (Odonata) of the Southwest
She has also coordinated with Tim Manolis to write the first dragonfly coloring book: Dragonflies of North America, a Color and Learn Book with Activities
Kathyâ€™s love of dragonflies was fostered when she built a wildlife pond. Visit the Bigsnest Wildlife Pond to find out about the other critters that have visited her pondsâ€¦.she has already developed a wildlife pond at her unfinished retirement home!
The coloring book and the publication Build a Pond for Wildlife are both available on CDs. Her current project is creating an E-book which will update the soon-to-be out-of-print Southwest Guide. All of her publications are available through her websites, and parks and bookstores, including Amazon.com.