Garden Good Guys
by Nanette Londeree, Master Rosarian
Is it a bird? Is it a plane? Is it a dragon? Is it a fly? What in the world is a Dragonfly? These unique creatures obviously aren’t birds, planes, dragons or flies. They are extraordinary insects that predate dinosaurs by over 100 million years and birds by some 150 million. In fact, a fossilized dragonfly from 250 million years ago was found to have a wingspan of 28 inches! Fortunately, present-day dragonflies are considerably smaller.
Easily recognized for their rather ethereal beauty, the “dragon” portion of their name comes from their fierce jaws that they use to catch their flying prey. The “fly” portion of their name is apt – they are the world’s fastest insects, capable of reaching speeds of up to 60 mph. They have some other colorful, descriptive names – “mosquito hawks” because they catch and eat so many mosquitoes and “devil’s darning needle” because of its body shape.
Dragonflies and their smaller counterparts, damselflies, feed on insects like gnats, mosquitoes, midges, flies, butterflies and moths and even other, usually smaller dragonflies. Near water, they will eat anything small enough that moves – water beetles, small fishes, salamander larvae and smaller dragonfly larvae. They don’t suck blood and they don’t bite or sting humans; they don’t have any device to sting with. Why are these insects beneficial to the rosarian? While they may not be predators of insects that are primarily pests of roses, their appetite for mosquitoes alone provides the rosarian with a more comfortable and safer environment to garden in.
Dragonflies are insects belonging to the order Odonata which is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body. They are distributed throughout the world with more than 5,000 described species. They are robust insects ranging in body length from 1 to 4 inches. The adults are often brightly colored and have a long slender abdomen. They have two pairs of almost equally sized long thin membranous wings; both pairs of wings usually have a stigma (a dark or colored patch near the middle of the leading edge) and can flap or beat their wings independently. The wings do not fold and are held outstretched when at rest. They do have strongly biting mouthparts and are active and aggressive carnivores, both as adults and as young (called nymphs).
Dragonflies have very good eyesight due to their unique eye structure. Their eyes have up to 30,000 facets; each one is a separate light-sensing organ arranged to give nearly a 360° field of vision and enable them to detect even the slightest movement.
Dragonflies employ a particular optical illusion, termed motion camouflage, to stalk other insects that invade their territory. A dragonfly can move in such a way as to project itself as a stationary object while speedily attacking its victims.
The life cycle of the dragonfly, from egg to death of adult, varies from six months to as much as six or seven years. Female dragonflies lay eggs in or near water, often in or on floating or emergent plants. Most of the life cycle is spent in the larval form, beneath the water surface, using internal gills to breathe. The nymphs are not pretty like the adults; they have robust bodies that are somewhat bullet-shaped. They have tiny wings and a large lower lip, which they use to catch their prey. When the nymph reaches maturity, it crawls out of the water onto a plant stem. The outer skin of the nymph splits along the back of the thorax and the young dragonfly emerges. Over the next few hours the insect will undergo its maiden flight, often a short relatively floppy flight away from the water, when both the wings and body have sufficiently hardened. During this maturation, the males of some species undergo dramatic changes in coloration. It takes about two days before the adult dragonfly’s beautiful colors are fully developed. Adult dragonflies (called imagos) can live up to two months if not caught by predators.
Apart from mankind, dragonflies don’t have many enemies. Unlike butterflies, they are not attracted to flowers and they don’t eat nectar. In order to encourage them to frequent our garden you can put in a small pond – even a wooden half barrel can work. Whatever the size of the pond, it should be located where it will be protected from wind and will get midday sun. Ideally, it should vary in depth, shallow at the edges and at least two feet deep in the center, and include a variety of water plants. If possible, put a few flat rocks near the pond’s edge. Dragonflies like to warm up by basking in the sun.
Although experts say that about 15 percent of North America’s 307 dragonfly species are in danger of extinction, the dragonflies at greatest risk for extinction are the stream dwellers, species that won’t be attracted to your backyard pond. Craig Tufts, chief naturalist for the National Wildlife Federation says “You can help protect their habitats by supporting laws and practices that reduce water pollution and protect riparian areas; you’ll be helping a lot of other creatures in the process.” If you’re fortunate enough to have these lovely creatures in your garden, enjoy their beauty and help protect their environment.
Photo by Edmund JP, used with permission from:
http://www.istockphoto.com/