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 youโre 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 otherโs lifestyle.
Overview of the differences between dragonflies and flies
Below is a table that summarizes several important differences between the two insect Orders. Because the terms โdragonflyโ and โflyโ both cover a huge and diverse variety of creatures, Iโve narrowed each insect type to an example species to illustrate the differences.ย
Dragonflies | Flies | |
Order | Odonata (oh-doh-nah-tah) – means “toothed” | Diptera (dip-tair-ah) – means “two-wings” |
Approximate number of worldwide identified species | 5,600 | 150,000 |
Size range | 1.4 – 3.7 inches (3.6 – 9.4 cm) | 0.28 – 0.31 inches (0.7 – 0.8 cm) |
Body shape | Long, thin body with large head and thorax and elongated abdomen tapering to a point | Short and compact, thorax and abdomen about the same length |
Wing configuration | Two (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 โhalteresโ. 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 structure | Chewing | Mostly sucking, sponging and lapping. Some species chewing. |
Leg structure | Perching, grasping | Walking, standing |
Colors | Species 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 habitat | Specialist: Lakes, ponds, quiet portions of rivers with heavy vegetation | Generalist: All areas associated with humans and human-raised livestock (โsynanthropicโ) |
Lifestyle | Predator | Scavenger |
Development | Incomplete metamorphosis (“hemimetabolism”) | Complete metamorphosis (“holometabolism”) |
Species example | Libellula vibrans (“Great Blue Skimmer”) | Musca domestica (โHouse flyโ) |
Dragonflies and flies have different body shapes
A dragonflyโs 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 and flies are different sizes
They are also very different sizes. Dragonflies are huge compared to flies; the Great Blue Skimmer is about 8 times bigger than a House Fly. In fact, dragonflies may be as big and heavy as an insect can become and still fly in todayโs atmosphere.
Dragonflies and flies are different colors
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.
Dragonflies and flies have different wing configurations
After size, the number of wings and their positioning probably stand out as the most visible differences between the two types of insects. All dragonflies have four wings; all flies have only two.
Dragonflies hold their wings straight out horizontally, which gives them a distinctive t-shaped silhouette. Flies have only two wings which lie on top of their thorax and extend slightly out to the side in a triangular silhouette.
Dragonflies and flies fly differently
The wing differences go beyond the cosmetic; the two types of insects actually fly differently.
The Great Blue Skimmer – like all dragonflies – flaps its front wings independently from its hind wings, which lets each pair catch undisturbed air.
Additionally, the dragonfly twists each wing on the down stroke of each flap, โcreating 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, 68)
This is a unique mode of flight in the living world and has been studied extensively. The House Fly flies in a more usual manner, flapping both wings at the same time to generate lift.
Dragonflies are fighter pilots; flies are 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 the House Fly can perform an acrobatic trick that the Great Blue Skimmer canโt – it can turn itself upside down in midair.
A House Fly beats its wings much faster than a dragonfly does – approximately 1000 beats per second versus a dragonflyโs 20-40 (Tenneson 2009). When combined with lightning fast information about air currents and the insectโs position in space supplied by the halteres, this fast wing speed allows a House Fly to flip itself over completely in mid-air without falling from the sky.
Flies usually perform this maneuver to land upside down on a surface. Special pads covered in sticky secretions on their feet grip their landing surfaces. These adaptations allow House Flies to cling securely to nearly any surface.
By contrast, dragonflies must stay upright.
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 flies at a comparatively pokey average speed of about 4.5 miles per hour (7.2 kilometers per hour) (Dahlem 2009).
Dragonflies and flies have different mouths
Skilled predators, dragonflies hunt on the wing, snatching flying insects out of the air. Their jaws (or โmandiblesโ) 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 decaying organic matter by lapping up liquid. They have no need for strong jaws like the dragonflies so their mouths have developed sponging mouth parts instead.
Dragonflies perch; flies walk
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.
For more information, check out this Now I Wonder post “Can dragonflies walk?“.
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.
Complete versus incomplete 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 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.
Dragonflies are good neighbors; flies cause problems
Dragonflies and flies live very different lifestyles.
Dragonflies live near quiet, fresh water which supports abundant populations of flying insects. They chase these insects down for food and donโt 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.
Different insects; fascinating abilities
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.
Imes, Rick. 1992. The Practical Entomologist. London: Quarto Publishing.
Meyer, John. North Carolina State University, NC State General Entomology, https://projects.ncsu.edu/cals/course/ent425/library/compendium/odonata.html
Tennessen, K. J. “Odonata.” In Encyclopedia of Insects, edited by Vincent H. Resh, and Ring T. Carde. 2nd ed. Elsevier Science & Technology, 2009.