Of the more than 300 in North America, none are more interesting than the black saddlebags dragonfly (Tramea lacerata), so named because of the black patches on its hind wings. When viewed from above, the patches look to be resting on each side of the abdomen, resembling saddlebags draped across the back of a horse.

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Naturalists first wrote about dragonflies in the 1500s, but the fossil record for dragonflies stretches back more than 300 million years. In other words, dragonfly relatives patrolled the skies 70 million years before the first dinosaurs appeared!

Five hundred years ago, scientists thought that adult dragonflies were a difference species from their larvae. This belief is not completely baseless: Adult dragonflies are winged fliers, while their larvae swim in water and breathe through gills. However, in 1669, the Dutch biologist Jan Swammerdam used a microscope to prove that dragonflies started as eggs, developed into larvae and finally became adult dragonflies.

Black saddlebags life cycle

A female lays eggs in a pond, marsh or other still water. Each egg hatches into a nymph (also called a naiad)—a squat, six-legged aquatic bug with an oval body, spindly legs, and developing wings folded on its back. Each nymph breathes through internal gills by pulling water into a chamber in its rectum. There dissolved oxygen passes across thin, folded tissues and enters the respiratory system. The nymph then expels the water. If it senses danger, the nymph can expel the water with enough force to propel itself through the water like a miniature jet ski.

Another unusual feature of these nymphs is an extendable lower lip, folded underneath the head. When prey swims within reach, the nymph shoots the lip out, grabs the victim with a pair of hooked appendages on the lip, and pulls the prey in like a fishman (or woman) reeling in a line.

When the , it crawls out of the water and up a plant stem. Its skin splits open and an adult dragonfly slowly crawls out. The dragonfly pumps fluid through the veins in its crumpled wings, expanding them. Once the wings and body have hardened, it flies away, leaving behind its empty skin. 

Black saddlebags spend much of their day flying, rarely perching—even while feeding. Because of this, they have developed an unusual way of : while flying, to cool their body, they lower their abdomen into the shadow cast by the dark patches on their wings. They also cool themselves by gliding rather than beating their wings, which reduces the amount of heat their body produces. In addition, they increase the circulation of hemolymph (insect blood) to the abdomen, which has a large surface area and cools more quickly than other parts of the body. When the temperature reaches 95°F or more, the heat is too much even for these hardy dragonflies, and they find a cool place to rest.

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The black saddlebags dragonfly is one of only 18 North American dragonflies that migrates. However, not all of these dragonflies migrate. 

In late summer or fall, the migratory saddlebags fly to the southern United States or even to Mexico, where they reproduce. The adult offspring live throughout the winter in the south, and lay eggs that grow into adults that fly north to our region in the spring. These spring dragonflies may arrive before overwintering saddlebags larvae have transformed into adults.

This means that a black saddlebags dragonfly you see now may not have spent its entire life in this region. It may have migrated from the south. Of course, it’s also possible that it spent its whole life here. Scientists have not documented the black saddlebags’ complete migratory pattern nearly as well as that of the common green darner dragonfly, but they can use techniques, such as stable-hydrogen isotope analysis, to determine where these insects grew up. 

Mosquito Control

Black saddlebags dragonflies—both nymphs and adults—are good at controlling mosquito populations. Dragonfly nymphs may eat on average 40 mosquito larvae per day. Adults catch and eat mosquitoes in mid-air. Male saddlebags dragonflies may even form swarms to gobble up mosquitoes.

So, the next time you see a black saddlebags dragonfly, remember its astonishing history. Its ancestors flew millions of years before the first dinosaurs appeared and have survived mass extinctions, ice ages and shifting continents. What a remarkable little creature it is.

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