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Common Name: Dragonfly, Horse stinger, Devil's needle, Ear cutter, Adderbolt - The etymology of the name Dragonfly has not been clearly established; however, the dragon has long been used in Christian symbolism to evince the devil. This suggests the etiology that the seemingly magical acrobatics of the dragonfly could only be attributed to satanic influence. The demonic analogy is supported by names that elicit similar malevolent intent: attacking animals and humans and association with adders (snakes).
Scientific Name: Order Odonata - The order is named for the Greek word odon, meaning tooth; the dragonfly has pronounced mandibles (jaws) that they use to great effect in predation. Suborder Anisoptera - The suborder is from the Greek anisos meaning not (an-) equal (-isos) and ptera meaning wing; dragonflies have unequal wings, the back wings are broader at the base than the front wings.
Dragonflies are among the most primitive forms of life; they have survived the vicissitudes of changing climate over the course of geologic million-year lapses. The earliest fossils are of the Protodonata and Protoanisoptera, extinct groups that lived in the Carboniferous Period, about 325 million years ago. These pre-dragonflies were generally larger, some with wingspans of almost a meter; they are often depicted in flight over artists' conceptions of the primordial swamps that engendered the coal and oil deposits that we now depend on for energy. It is hypothesized that higher levels of oxygen due to the profligacy of land plants contributed to their Antaean dimensions.
The first "modern" odonates appeared in the Permian Period about 250 million years ago, their size reduced to that of their present-day progeny. There are currently 2,874 species of dragonflies worldwide with 316 in North America; the range and dispersion of individual species in part attributable to the breakup of the supercontinent Pangaea at the end of the Paleozoic Era. There is some debate as to whether dragonflies had then yet evolved into their current from, as no fossilized larval forms have been found; modern dragonflies have an aquatic nymph phase. Aside from the size, very little has changed in the millennia since the dragonfly first appeared on the biological stage.
Dragonflies have a simplified and perhaps primitive life cycle compared to other related insects; they are hemimetabolous, passing from egg to larva to adult without the customary pupa stage of butterflies and beetles. The majority of a dragonfly's life is spent as an aquatic larva; over a two to six year period, the larva molts to form from six to fifteen instars (intermediate stages). Dragonfly larva are voracious predators and will capture and eat anything that falls within the constraints of physical size - that includes other dragonfly larva of their own species. They have evolved a especially effective adaptation to this end. The lower lip or labium is a folded appendage that extends under the head and thorax. When a potential target is detected, the labium is rapidly extended (like the tongue of a frog) and the prey is grabbed with hand-like palpi and drawn into its powerful mandibles. The larva's propulsive movement is also relatively unusual; it draws water into its anus and uses the muscles of the rectum to produce water jet locomotion. Once mature, the nymph crawls out of the water on an aquatic plant stem, the skin splits, and the delicate adult emerges to carefully expand the metamorphosed wings.
The most notable feature of the adult dragonfly is the rigid wing structures which cannot be retracted or folded but rather jut out at right angles like the wings of a biplane. Each of the dragonfly's wings is controlled by a separate muscle that is attached directly to the thorax; more advanced flying insects like wasps have the rear and front wings controlled by the same muscle which indirectly operates the wings by distorting the thorax. The more primitive wings of the dragonfly are far from inferior; they need only flap at about 30 times per second (compared to about 600 times per second for a mosquito and 1000 times for a fly) due to the power imparted by the individual musculature. The independence and strength of the dragonfly's wings is also evident in their gifted flying skills - they can fly straight up, hover for over a minute (limited by the necessity of flowing air to remove heat), and fly backwards with equally graceful skill. In reaching speeds of up to 45 miles per hour - that is about 100 body lengths per second - they can catch almost any prey and elude the most persistent predators.
Another factor that has contributed to the geological success of the dragonfly is its superlative eyesight. The huge eyes are conspicuously mounted at the very top and front of the head, a continuous surface that has the look of a radar dome on an airplane. The eyes can rotate through a full 360 degrees, and, like an entomological Argus, each eye has as many as 28,000 individual facets called ommatidia. Each facet is capable of seeing in a slightly different direction and projecting an image, the sum of the images providing a complete picture of the surrounding environment; it is estimated that over 80 percent of the insect's brain is dedicated to processing the aggregate visual data. The eyes are so effective that the dragonfly has almost non-existent antennae, relegated to a secondary tactile role; they are able to see their gnat-sized quarry at a distance of over 100 feet.
It is as a consummate predator that the adult dragonfly is most well endowed. The thorax - the part of the insect between the head and the abdomen - is rotated so that the attached legs are directed forward toward the mouth. This arrangement forms a sort of spiny box that is used as an aerial sieve to scoop up prey while flying, taking advantage of superior speed and maneuverability like an advanced jet fighter exterminating a glider. In addition, they are opportunistic, eating anything they can catch including flies, mosquitoes, butterflies, damselflies and other dragonflies; they even hunt in packs when there is an abundance of prey like swarms of flying ants. It is not surprising that the dragonfly has survived for over 200 million years; the combination of speed, sight and strength has ensured their success in eluding predators and in pursuit of prey even as these coeval life forms have evolved over time.
The dragonfly has a most unusual mating ritual, contrary to what one might consider appropriate for its evident evolutionary success - which would favor facility in addition to fecundity. The process starts with the production of sperm at the end of the abdomen of the male which he then repositions to the front of the abdomen, just behind the thorax. This "pseudo-genital" consists of a chitinous ventral plate called a sternite that has been modified with scoop-like structures and a priapic extension. The coital act is consummated when a male grabs a female just behind the head with pincers at the tip of his abdomen; this elicits a response from the female that is manifest in an arching of her abdomen in a loop to engage the male's deposited sperm. The interlocked pair then fly around like an animated winged pretzel. The reproductive mandate of the male goes well beyond manual control of the sexual act - males have specialized tools which they use to remove any sperm that may have been deposited by a rival male before injecting their own. In many species the female is then guarded by the male until the act of oviposition is completed to ensure that the hereditary traits are successfully transmitted to the offspring. The eggs are deposited on or near the water; the eggs hatch after a period that ranges from a week to several months.
The perception of the dragonfly varies from minatory to beneficent according to region, continent and culture. In Western cultures, the dragonfly is generally considered a harbinger of evil and is accordingly described in pejorative terms like devil's needle and ear cutter. This association is likely due to the superstitious personifications of good and evil that were common during the medieval period - Satan is said to have beset the world with dragonflies to spread ill will. Absent a demon-centric cultural mindset, the dragonfly occupies a much more benign place in the other cultures of the world, notably Asia. For example, in Japan the dragonfly is the symbol of just about everything one might consider as positive in terms of life's goals: happiness, success, courage and strength. Perhaps even more significantly, the dragonfly is the spirit of the rice plant, the main staple of the agricultural economy and the diet. The dragonfly's identity with Japanese culture extends to the name of its home territory - Japan was once known as Akitsushima, which means, literally, dragonfly island. . |
