The Intricacies of Dragonfly Flight

Photographing dragonflies is an alluring pursuit both because of their physical beauty and because of their mysterious, unmatched abilities on the wing. The difficulty of getting good pictures is part of the allure. For a still portrait you have to locate the subject and get close without startling it. Useful images of a dragonfly's aerial movements are even more elusive.

Spot-winged Glider

The defining spots for this species' name are scarcely visible when it is at rest. They are located at the rear of the hind wings, alongside the abdomen. In this photograph they seem only slight smudges on the reticulations of the wing membrane.

The flight picture above better shows the nominative spots, while suggesting the difficulty of obtaining a clear aerial image.

However, there was ample evidence in this series of stop-action photos to convince me that there is more to dragonfly flight than vigorous flapping of the wings.

The pictures show wings in various postures, angles, and sequences. I had to know more about this.

I found on line this eye-opening video study (viewer friendly but sophisticated = well-funded) of masterful physiology, The Insane Biology of: The Dragonfly. Printed below are excerpts from the transcript worth reading for a deeper appreciation of one of nature's marvels. Its mechanics are being closely studied by aeronautical engineers and assimilated into drone prototypes.

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Few other insects use direct flight muscles. Most winged insects have what are known as indirect flight muscles, which attach to the walls of the thorax, making the thorax deform as they expand and contract. The deformation of the thorax transmits its resonance to the wings, making them vibrate and initiate the flapping motion. While indirect flight muscles have their own advantages, dragonflies instead have individual muscles that attach directly to the base of each of their four wings. Being able to turn on each wing individually enables them to move and direct each of their four wings independently, in all three axes, meaning they can control their horizontal, vertical, and torsional motions, granting them precision and agility that is unparalleled by most insects with indirect flight muscles. Thanks to these independent controls, dragonflies are one of the few insects that can propel themselves in all six directions: left, right, up, down, forward, and even backward.

Another remarkable way that dragonfly flight differs from other insects is their ability to flap their fore and hind wings in different phases, and can vary that phase depending on maneuvers they wish to perform. One flight technique is known as counter-stroking, where they flap their fore and hind wings one hundred and eighty degrees out of phase with each other. This allows them to hover or engage in very slow forward flight, and can generate large amounts of lift.

For fast forward flight, they are able to switch to phased stroking, where the hind wings beat ninety degrees ahead in phase of the forewings. While this generates far less lift, it generates a lot more thrust, with some species being capable of reaching well over fifty kilometers an hour, making them by far the fastest flying insects.

Dragonflies can also engage in synchronized stroking, which is when the fore wings and hind wings flap together at the same time. This is most useful to increase their acceleration, and to prepare for turning or changing directions quickly. It allows them to generate huge amounts of lift, but can't be sustained for long periods of time, so they generally only use this configuration when chasing prey.

In addition, dragonflies are also capable of flying backwards, a flight maneuver that is not possible for almost any other animal, except a few other small types of flies and the hummingbird. They do this by tilting their bodies upward at ninety degrees, to change the direction of the force generated by the wings.

Finally, dragonflies can also choose to not flap their wings at all, allowing them to free glide, take advantage of an updraft, or, in the case of some female dragonflies, take a ride with a male who can hold onto her, making him beat his wings to propel the two of them.