Dragonflies: Beautiful hunters
By Bill Rhodes | Conservancy of Southwest Florida Volunteer
Visitors to the Conservancy of Southwest Florida are able to view or enter a variety of Florida ecosystems. The Smith Preserve, home to a large number of Gopher Tortoises, is typical scrub land; the Shotwell Waverly Family Filter Marsh is an estuarine environment and the Nature Trails meander through both hardwood hammocks and mangrove thickets.
Fresh or brackish water is close by in all cases, and guests see many diverse animals — birds, reptiles, fish, amphibians and insects. One animal ever present starts its life underwater, and, as it matures, leaves the water for the air, becoming one of the most efficient, swiftest flying and feared (if you are an insect) predators in the sky. It has remained essentially unchanged for well over 300 million years, and will likely go on for millions of years into the future.
Dragonflies, together with their close relatives the Damselflies, are in in the insect Order Odonata, and can be found in the fossil record as far back as the Carboniferous Period, some 325 million years ago. While their body plan has remained essentially unchanged, some of those ancient dragonflies grew to have wingspans of almost two and a half feet.
Today, there are about 5000 Odonata species throughout the world, ranging in wingspan from just under an inch to almost 8 inches.
As do all insects, they have three body parts (head, thorax and abdomen) and six legs. Dragonfly adults sport four strong, semi-rigid, veined wings and often have iridescent, shimmering bodies, with large compound eyes occupying most of their head.
Each wing can move independently, enabling the dragonfly to twist, turn and practically stop in midflight. Their mouthparts are modified so that they will snap out at flying insects at a speed faster than the hapless victim can react, snaring it and bringing it back to be eaten.
Unlike many insects, they go through only three life stages, not four (butterflies, for example, go through four — egg, larva or caterpillar, chrysalis or pupa, and then adult). The males and females mate in the air, and the female lays eggs on marsh plants or the surface of the water. When they hatch, the juveniles, called nymphs, move deeper into the water, staying on the bottom. They are truly aquatic, equipped with gills, and are wingless, looking nothing like the adult form. These nymphs are also ferocious predators, using their front legs and strong modified mouthparts to catch other small invertebrates, but will dine on just about anything they can catch, including tiny fish and tadpoles.
After a year or more, the nymph crawls onto a blade of grass alongside the water, and there it completes its transformation into a flying adult and takes to the air. They then begin patrolling the sky in search of other flying insects as food, which they spot with their enormous eyes, chase and usually catch.
Despite their adaptations to be fierce predators in the air, they are absolutely harmless to people, and are often strikingly colored and interesting to watch. Unchanged for hundreds of millions of years, they are the kings and queens of their aerial and aquatic worlds — highly efficient, often beautiful predators well worth pausing to observe.
