Parts of an insect ( useful vocabulary): Although the superficial appearance of insects is extremely varied, certain characteristics of their anatomy are common to the entire class. All mature insects have bodies composed of three parts: head, thorax, and abdomen (the abdomen and thorax are not always differentiated in larvae). Each of these parts is composed of a number of segments. The head is made up of several segments, usually so fused they are scarcely differentiated. On the head are two antennae; a pair of jaws, or mandibles; a pair of auxiliary jaws, or maxillae, that in turn bears a pair of palps; and a fused second pair of accessory jaws, the labium, that also bears a pair of palps. The antennae, usually attached to the anterior part of the head, are segmented. In some insects, the antennae carry organs of smell as well as organs of touch. The mandibles are large, heavy jaws on either side of the mouth. They close horizontally and are used for grasping food and crushing it. The maxillae, or inner jaws, are lighter in structure. The mouths of many insects are adapted for piercing and sucking rather than for biting. The eyes of the insect are also situated on the head. All insects have three pairs of legs, each pair growing from a different part of the thorax, called, from front to back, the prothorax, the mesothorax, and the metathorax. Many larvae have, in addition, several pairs of leglike appendages called struts, or prolegs. The forms of the legs vary, depending on their uses, but all insect legs are made up of five parts. In winged insects, the wings, usually four in number, grow from the thorax between the mesothorax and the metathorax. The upper and lower membranes of the wings cover a network of sclerotized tubes, called veins, that stiffen the wing. The pattern of veins of the wings is characteristic of most insect species and is extensively used by entomologists as a basis for classification.
Posted on: Mon, 02 Sep 2013 15:38:09 +0000
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