Dragonflies darted through the skies when dinosaurs roamed the earth. Below are three key factors which influence their lengthy survival.
Dragonflies of the order Odonata have managed to thrive throughout millenia. There have been fossils of prehistoric dragonflies found in France dating to 270 million years ago, their wing-span reaching almost three feet. In the present, dragonflies do not grow bigger than eight inches. Other than their size however, they are essentially the same insects that flew among dinosaurs.
The dazzling shapes and shades of every imaginable color have graced the bodies of dragonflies and captivated cultures throughout time. Their forms have inspired paintings, medieval manuscripts, floor tiles, stained glass, postage stamps and even Japanese bronzes as early as 300 BC. Their flight has instilled varied myths worldwide. Though new species are commonly found, there are currently more than 5,500 species of Odonata known to man.
A fly of a different color
Over the course of a dragonfly's life, which can last up to seven years, adaptation and many changes occur. Before they become winged adults they live underwater where they are born. As nymphs, they feed on aquatic animals for one to three years. Before leaving their water world they molt 10 times, enabling them to grow. Once emerged from water they still look quite ugly in comparison to their final form. They are at first a brownish or whitish color. The many stages in a dragonfly's life is perhaps representative of why they have been able to exist for generations.
Males and females have different color patterns within a species. For example, according to Philip S. Corbet, the female chromatype (color-type) of Ischnura graellsii or Iberian Bluetail, changes from light orange, to reddish-orange, to brown ochre as it ages. Color change for a male of the same species is entirely different and results in a brilliant blue. Each species passes down two or more color patterns. Dragonflies get their color from aging, genetics or are induced by temperature. All Odonates together span the entire color spectrum.
To see the world
Dragonflies are found worldwide except in frozen polar areas. On any continent take a look at any one of these aerial hunters and you will probably notice how large their eyes are compared to the rest of their body. Sight is an exceedingly vital sense for the dragonfly. They have over 20,000 six sided units in each eye to help them see. Most insects have about two dozen. Often catching prey in mid-air, their sight and agility are their main advantages.
Thermoregulation
In order to keep at a certain temperature, dragonflies need to thermoregulate, or keep their core body temperature within certain limits.
The thorax of dragonflies is insulated with air sacs to aid in thermoregulation. Some dragonflies can change their posture in order to thermoregulate. When too hot they elevate their thorax and abdomen to a vertical position, called obelisking, decreasing the amount of solar radiation received by the dragonfly.(Cochran, "Biological and Ecological influences on the Behavior of Dragonflies")
Metabolic heat production is controlled by alternating between “gliding” or “powered” flight. Some species are able to elevate their body temperature by “wing-whirring.”
The ability of dragonflies to maintain a relatively constant body temperature is determined primarily by climate, body size, and behavior.(Corbet, 1999)
Of damsels and dragons
Dragonflies are commonly mistaken for damselflies. There are over 2,600 species of the Suborder Zygoptera (damselflies), which along with the Suborder Anisoptera (dragonflies) make up the more than 5,500 species of Odonates.
The most noticeable difference is their wings. Damselflies, also usually smaller, fold their wings back close to the body at rest whereas dragonflies keep their wings spread out at about 180 degrees.
Images from National Geographic