Insect external structure
Insect internal structure
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Insect identification > Odonata
The Odonata are such large and noticeable insects that they have received many common names, such as dragonflies, snake doctors, devil's darning needles, snake feeders, etc. They are most plentiful near water, as in this they spend their early lives, though the larger and more powerful members of the group are frequently seen flying high in the air and at some distance from their more usual habitat.
The dragonflies have rather long, slender bodies, the abdomen being less shortened by the fusion and telescoping of its segments than in most insects. The head is large, generally rather spherical, though concave behind, and a great part of its surface is occupied by two very large compound eyes, each of which, in some species, contains more than thirty thousand facets. As these insects are carnivorous and capture their prey as it is flying, the advantage of large eyes which are also, because of the curvature of the surface of the head, capable of seeing in almost every direction is evident. There are also three ocelli. The antennae are short and not very noticeable.
The mouth-parts, which are of the chewing type, are large and well developed. The food appears to be captured by the legs and held by them while it is being eaten. Four wings are present, all of about equal size, though the hinder pair are somewhat larger except in the section known as the damsel flies. The main veins are stout and are connected by many cross veins. Near the middle of the costa of each wing is a slight notch called the nodus, at which point there is a particularly stout cross vein. When at rest the wings are held either nearly vertical over the body (damsel flies) or extended laterally, much as in flight. The metamorphosis is by progressi ve changes at times of molting; and though the nymph can hardly be said ever to greatly resemble the adult, development may be considered as being by an incomplete metamorphosis.
The Odonata may then be characterized as:
Insects which as adults usually have long, slender bodies, large heads and large eyes; wings four, membranous, the hinder pair as large as or larger than the front pair, and each has near the middle of its. front margin a notch, somewhat resembling a joint, called the nodus; mouth-parts for chewing and well developed. Metamorphosis incomplete.