Dragonfly eating an insect while perched on grass. Photograph taken by the author. Copyright Now I Wonder.

Are Dragonflies Actually Flies? Complete Guide To The Answer

Have you ever wondered if dragonflies are actually flies? After all, the word “fly” is literally included in the name “dragonfly”. And if not, why call them dragonflies? If youโ€™re wondering this too, this post will help.

Dragonflies and flies are unrelated insects. Dragonflies are much larger than flies and have four wings compared to flies which have only two wings. Flies undergo complete metamorphosis while dragonflies undergo incomplete metamorphosis. They live in different habitats and have different lifestyles.

Dragonflies and flies are superbly adapted to their respective niches in the natural world. Each would starve to death if forced to live the otherโ€™s lifestyle.

Classification

Dragonflies and flies are both types of insects so belong to class Insecta. But they differ from each other significantly, so scientists classify them in different orders within class Insecta.

Dragonflies belong to order Odonata and suborder Anisoptera, while all fly species belong to order Diptera.

Worldwide, there are far more species of flies than of dragonflies. Scientists have identified more than 17,000 fly species in North America alone, but only 300 dragonfly species north of Mexico (Eaton and Kaufman, 2007).

A note about the flies discussed in this post

With more than 17,000 species living in North America alone, flies are astonishingly diverse.

Unlike different dragonflies, which are easily identified as “dragonflies” even when they differ in color and size, many fly species look very different from each other. Some may not be recognized as “flies” at all and others are easily confused with other kinds of insects.

For example, many people are familiar with mosquitoes and midges but may not realize that they are fly species. Additionally, flower flies classified in family Syrphidae mimic bees and wasps to an astonishing degree.

Because of this diversity, the picture that forms in most people’s minds when they think of a “fly” is more likely to resemble a house, blow, or flesh fly species (families Muscidae, Calliphoridae, and Sarchophagidae respectively). Therefore, to keep things simple, this post focuses on comparing dragonflies to flies in these families and sets aside the lesser known goups like biting flies, predatory flies, and parasitoid flies.

Overview of dragonflies vs. flies at the order level

Below is a table that summarizes several important differences between the two insect Orders. Because the terms โ€œdragonflyโ€ and โ€œflyโ€ both cover a huge and diverse variety of creatures, Iโ€™ve narrowed each insect type to an example species to illustrate the differences. 

DragonfliesFlies
OrderOdonata (oh-doh-nah-tah) – means “toothed”Diptera (dip-tair-ah) – means “two-wings”
Sub-orderAnisopteraCyclorrhapha
Approximate number of worldwide identified species within the order5,600150,000
Body shapeLong, thin body with large head and thorax and elongated abdomen tapering to a pointShort and compact, thorax and abdomen about the same length
Wing configurationTwo (2) pairs of large, elongated membranous wings.

Wing pairs are similarly sized.
Wings are held at approximately 90 degrees to the long axis of the body at rest, within the same plane.

All wings contribute to powered flight and maneuverability.
One (1) pair of tapered membranous wings.

Hind wing pair are vestigial sensory organs called โ€œhalteresโ€.

Wings are held at approximately 30 degrees to the long axis of the body at rest, within the same plane.

Only the fore wings contribute to powered flight. Halteres stabilize the body and send sensory information about air currents and speed during flight. 
Mouth structureChewingMostly sucking, sponging and lapping.
Some species chewing.
Leg structurePerching, graspingWalking, standing
ColorsSpecies and sex dependent.
Can be bright blue, green, yellow, bright red, brown and black.
Wings can be transparent or translucent or display dark patches.
Species dependent.
Thorax is striped with black and gray, abdomen is brown. Wings are translucent.
Some species can be iridescent green or blue.
Common habitatSpecialist: Lakes, ponds, quiet portions of rivers with heavy vegetationGeneralist: All areas associated with humans and human-raised livestock (โ€œsynanthropicโ€)
LifestylePredatorScavenger
DevelopmentIncomplete metamorphosis (“hemimetabolism”)Complete metamorphosis (“holometabolism”)
Species exampleLibellula vibrans (“Great Blue Skimmer”)
Musca domestica (โ€œHouse flyโ€)
Overview of differences at the order level of classification.

Anatomy

Diagram of common characteristics of dragonflies order Odonata. Diagram and photograph by the author. Copyright Now I Wonder.
Diagram of common characteristics of dragonflies order Odonata Diagram and photograph by the author Copyright Now I Wonder
Photograph of a true fly labelled with important field marks that identify insects in order Diptera. Photograph and diagram by the author. Copyright Now I Wonder.
Photograph of a true fly labelled with important field marks that identify insects in order Diptera Photograph and diagram by the author Copyright Now I Wonder

Body shape

Dragonflies and flies have different body shapes, which make them very easy to distinguish from each other.

A dragonflyโ€™s body is very long and thin, with a large thorax (where the legs and wings attach) and a narrow, extended abdomen. A fly’s body is much shorter and stockier overall.

Dragonflies are also huge compared to flies; a Great Blue Skimmer dragonfly (Libellula vibrans) is many, many times larger and heavier than a House Fly (Musca domesticus).

Great Blue Skimmer Dragonfly insect Libellula vibrans. Photograph taken by the author. Copyright Now I Wonder.
Great Blue Skimmer Dragonfly insect Libellula vibrans Photograph taken by the author Copyright Now I Wonder

Dragonflies come in a dazzling array of colors, including brilliant greens, browns, blues and reds. Male Great Blue Skimmer dragonflies are a striking pale blue with bluish-green eyes, while females are a reddish brown with a black stripe down the abdomen.

House Flies, on the other hand, are mostly black and gray, although they can appear tinged with green in certain lights. Other fly species may show iridescent green and blue coloration but in general, flies are much duller.

Fly perched on a leaf. Insect order Diptera. Photograph taken by the author. Copyright Now I Wonder.
Fly perched on a leaf Insect order Diptera Photograph taken by the author Copyright Now I Wonder

Feet and legs

Leg anatomy differs between dragonflies and true flies.

Although both types of insect have six legs, their legs are very different in both structure and function.

Dragonfly legs are crowded together at the front of their thoraxes, and end in claws. Both adaptations help them perch but limit their ability to walk. Sharp spines line their legs and help dragonflies control prey while hunting. Dragonflies swing their legs forward in flight to form a basket a split second before they physically scoop their prey from the air. Their leg spikes prevent the prey from slipping away.

Carolina Saddlebags Dragonfly Tramea carolina insect. Photograph taken by the author. Copyright Now I Wonder.
Carolina Saddlebags Dragonfly Tramea carolina insect Photograph taken by the author Copyright Now I Wonder

In contrast, the legs of most familiar flies, like the House Fly (Musca domestica) and blow flies (family Calliphoridae) are widely spaced and end in special, sticky pads. This anatomy makes flies extremely good at crawling around and allows them to cling securely to nearly any surface, even when upside down on plate glass.

Fly perched on a leaf. Insect order Diptera. Photograph taken by the author. Copyright Now I Wonder.
Fly perched on a leaf Insect order Diptera Photograph taken by the author Copyright Now I Wonder

Ground mobility

Both dragonflies and house flies can perch on their hind-most four legs and use their front legs to perform various tasks. Dragonflies use their front legs to hold and manipulate prey, whereas house flies use them to clean dust and debris off their body bristles.

But flies and dragonflies move very differently when grounded; flies can move easily across a surface while dragonflies have difficulty moving at all.

The legs on all dragonfly species crowd together towards the front of their thoraxes. This adaptation allows space within their thoraxes for the huge flight muscles that power the dragonflies’ long, narrow wings.

The positioning of their legs allow dragonflies to swing all six legs forward during attack on prey, scoop the insects out of the air and grip them until the dragonflies can grab them with their jaws. But this clustered arrangement limits the mobility of its legs when not in the air and prevents dragonflies from walking easily.

By contrast, house flies walk easily on widely spaced legs adapted for moving around on foot. A House Fly has two choices for moving from one location to another; it can either walk or fly. A dragonfly doesn’t have this choice; a dragonfly basically has to fly to get anywhere at all.

Feeding and mouth anatomy

Dragonflies are skilled aerial predators and hunt their prey on the wing. They intercept flying insects in mid-air, snatch them with their spiky legs, and bite the prey with their mandibles. Dragonfly jaws (or โ€œmandiblesโ€) are large, serrated, and powered by strong muscles perfect for slicing through the hard exoskeletons of their insect prey.

On the other hand, House Flies are scavengers that feed on soft, decaying organic matter. They have no need for strong biting jaws like dragonflies. Instead, these flies eat by lapping up liquid with specially evolved sponging mouth parts.

Flight style and mechanics

Wing configuration

Another major difference between dragonflies and flies is their wings.

First, dragonflies have more wings than flies. All dragonflies have four, large wings arranged in two pairs: a pair of forewings and a pair of hind wings.

In contrast, all flies have only two flight wings.

As an order, flies started out with two pairs of wings. But over the course of their evolution, their second pair reduced into structures called “halteres”. Halteres project from flies’ thoraxes as small knobs and play no part in powering flight. However, scientists believe that they provide sensory information during flight that helps flies orient themselves in mid-air.

Second, the configuration of their wings differs.

Dragonfly wings project out to their sides; they hold their wings horizontally. This gives dragonflies their famous and unmistakable T-shaped silhouette.

In comparison, the wings of fly species anchor on top of their thoraxes and extend out to the side only slightly. This gives flies a triangular silhouette.

Wing differences between dragonflies and true flies go beyond the cosmetic. These two types of insect fly differently.

Wing beat coordination and speed

Dragonflies like the Common Green Darner (Anax junius) flap their front wings independently from its hind wings. The beat of each pair of wings is slightly offset, which lets each pair catch undisturbed air and generates lift.

Common Green Darner dragonfly Anax junius in mid-flight. Photograph taken by the author. Copyright Now I Wonder.
Common Green Darner dragonfly Anax junius in mid flight Photograph taken by the author Copyright Now I Wonder

Additionally, the dragonfly twists each wing on the down stroke of each flap, โ€œcreating miniature whirlwinds that allow air to move much faster over the upper wing surface, reducing the air pressure there and greatly increasing lift.โ€ (Imes 1992)

Scientists have studied this unique mode of flight extensively with high speed photography and much research.

On the other hand, flies have only one set of wings to work with. They flap both wings simultaneously to generate lift.

A House Fly beats its wings much faster than a dragonfly doesโ€”approximately 1000 beats per second versus a dragonflyโ€™s 20-40 (Tenneson 2009).

Agility in flight

Both dragonflies and true flies fly incredibly well. But they differ in the maneuvers they can perform while in flight. In general, dragonflies can be considered fighter pilots and flies acrobats.

Both dragonflies and flies are superb aerialists and can hover, fly backwards, and change directions in midair faster than the human eye can follow.

But many flies can perform an acrobatic trick that dragonflies can’tโ€”flipping upside down in midair.

When combined with lightning-fast information about air currents supplied by tiny sensory hairs and the positional stability supplied by the halteres, some flies such as the House Fly (Musca domestica) can flip themselves over in mid-air without falling from the sky.

In contrast, dragonflies stay upright in flight.

Flight speed

Dragonflies may not be able to turn somersaults on the wing but they are speed demons in the air. Dragonflies can zoom around their territories at speeds up to 35 miles per hour (56 kilometers per hour) (Imes 1992, 68).

The House Fly (Musca domestica) flies at a comparatively pokey average speed of about 4.5 miles per hour (7.2 kilometers per hour) (Dahlem, 2009).

Metamorphosis

Dragonflies undergo incomplete metamorphosis, which means that they share some of the same physical structures at all life stages. Immature dragonflies have six legs, the same three body segments and very large eyes as the adults, and wing buds.

While different from adult dragonflies in many ways, you can recognize these immature insects as “dragonflies” if you know what to look for.

But flies undergo complete metamorphosis. This means that immature flies look completely different from adults. Known as maggots, larval flies look like worms, with soft, unsegmented, legless and headless bodies. Identifying a maggot as a “fly” based on its appearance is difficult.

Impact on humanity

Dragonflies and flies live very different lifestyles. Dragonflies are good neighbors; flies cause problems.

Dragonflies live near quiet, fresh water which supports abundant populations of flying insects. They chase these insects down for food and donโ€™t bother people. They cause cause no harm to humans. In fact, their appetite for eating huge enormous numbers of other insects benefits humanity since many of the species they feed upon do damage humans. For example, flies.

Flies live worldwide in all habitats because their food is easy to come by. As scavengers, they need only to locate sources of their preferred food, land, and feast.

Unfortunately, flies are not picky. They make no distinction between landing on a rotting rat as your picnic lunch and alternate happily between the two as needed.

Despite being admirable in many respects, flies can and do hurt thousands of people every year. Some species, like the House Fly, transmit diseases with their sticky feet. They land and walk around on decaying organic matter. Dangerous microorganisms cling to their sticky feet. The flies then transport these microorganisms to other locations, such as onto human food or even onto humans directly.

Other fly species such as black flies, horse flies, and deer flies evolved biting mouth parts, which they use on humans. And of course, mosquitoes- which are also flies- infect millions of humans every year with various deadly diseases, such as malaria, dengue, encephalitis, and yellow fever.

Conclusion

Dragonflies and flies are totally different creatures who have different skills, behaviors and lives. But they share one very important trait – they are both fascinating residents of the natural world.

References

Dahlem, Gregory A. “House Fly.” In Encyclopedia of Insects, edited by Vincent H. Resh, and Ring T. Carde. 2nd ed. Elsevier Science & Technology, 2009.

Eaton, Eric R. and Kaufman, Kenn. 2007. Kaufman Field Guide to Insects of North America. Mariner Books; Harper Collins.

Imes, Rick. 1992. The Practical Entomologist. London: Quarto Publishing.

Tennessen, K. J. “Odonata.” In Encyclopedia of Insects, edited by Vincent H. Resh, and Ring T. Carde. 2nd ed. Elsevier Science & Technology, 2009.

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Christine
Christine is the creator and author of NowIWonder.com, a website dedicated to the animals and plants that share our world, and the science that helps us understand them. Inspired by lifelong exploration and learning, Christine loves to share her knowledge with others who want to connect with wild faces and wild spaces.

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