Order Odonata Essay, Research Paper

The order Odonata is divided into three suborders: The Zygoptera, or damselflies, which can fold their wings over their abdomen, the Anisoptera or Dragonflies which can’t, and thus hold their wings straight out from their thorax, and the Anisozygoptera, an ancient suborder possible once containing the seeds of both the other 2 more modern suborders but now containing only two species from Japan.

You are likely to see plenty of dragonflies as you go out into the field in late summer, normally near water. They are more common in warmer parts of the world. In this order, the dragonflies have strong biting mouthparts and are active and aggressive carnivores, both as adults and as young, which are called nymph. They prey mostly on other insects. The adults have really large eyes, which may contain up to thirty thousand individual lenses or ommatidia. Because of these large amounts of lenses, dragonflies have exceptionally great eyesight and have been known to respond to stimuli up to forty feet away. Though they may have great eyesight, they have poorly developed antennae.

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 a mass of cross veins giving them the appearance of a mesh-like material. Unlike most insects, which either flap both pairs of wings in unison, for example bees and butterflies, or only flap the hind pair, beetles, or only have one pair, flies, dragonflies can flap or beat their wings independently. This means the front wings can be going down while the back ones are coming up. You can see this happening if you watch closely. Dragonflies are excellent flyers, and can even fly backwards.

Dragonflies are a very ancient order of insects. Fossils exist from more than 300 million years ago. Dragonflies are also relatively large insects, even now, but in they past they were much larger. Fossil remains of some of the largest flying insects to have ever existed are Dragonflies; one species Meganeura monyi had a wingspan up to 75 cm. The largest Dragonfly in the world now is actually a Damselfly (Zygoptera), Megaloprepus caerulata, from Costa Rica with a wingspan of 19.1 cm or 7.52 inches and a body length of 12 cm or 4.72 inches. Tetracanthagyna plagiata, from Borneo, is the largest Anisopteran, or true Dragonfly. The smallest is probably Agriocnemis naia from Burma with a wingspan of just 1.76 cm or .69 inches.

Dragonflies are unique in the insect world in that the male possess a set of secondary sexual organs on the second abdominal segments as well as his primary sexual apparatus on the ninth segment at the end of his abdomen. Mating commences with the male grasping the female with his abdominal claspers. The pair then assumes the wheel position with the tip of the female?s abdomen and her sexual apparatus engaging the male?s secondary copulatory apparatus. The male first uses his penis to remove any sperm left by a previous male before inseminating her himself.

Copulation can take from several minutes to several hours depending on species. The male stays in tandem with the female in many species while she lays her eggs.

Eggs are laid either inside the living tissue of a plant, endophytically, or into or onto the water or the mud of the bank, exophytically. Eggs are normally laid in batches. Endophytically laying species tend to be limited to several hundred or less eggs per day and exophytically laying species can lay several thousands per laying episode.

Dragonflies are eaten as larvae by fish, mainly bass, water shrews, water beetles, water bugs, and birds, particularly diving ducks. Dragonfly nymphs will also happily at each other. It is hard to believe that these beautiful and colorful animals can have any enemies. It is a shame how man can destroy such a unique creature of nature.

Earth-Life Web Productions. 24 February 2000. http://www.insectworld.com/main/odonata.html