WAYS AND MEANS OF LIVING
mouth parts fitted for sucking, or for piercing and sucking. Some of the sucking types of mouth parts will be described in other chapters (Figs. 121, 163, 183), but it will be seen that all are merely adaptations of form based on the ordinary biting type of mouth appendages. The fossil records of the history of insects show that the sucking insects are the more recent products of evolution, since all the earlier kinds of insects, the cockroaches and their kin, have typical biting mouth parts.
The principal thing to observe concerning the organs of feeding, in a study of the physiological aspect of anatomy, is that they serve in all cases to pass the natural food materials from the outside of the animal into the alimentary canal, and to give them whatever crushing or mastication is necessary. It is within the alimentary canal, therefore, that the next steps toward the final nutrition of the animal take place.
The alimentary canal of most insects is a simple tube (Fig. 68), extending either straight through the body, or
Fig. 68. The alimentary canal of a grasshopper
AInt, anterior intestine; An, anus; Cr, crop; GC, gastric caeca, pouches of the stomach; Hphy, hypopharynx (tongue); Lb, base of labium; Mal, Malpighian tubules; MInt, mid-intestine; Mth, mouth; Oe, oesophagus; Rect, hind intestine (rectum); SlGl, salivary glands opening by their united ducts at base of hypopharynx; Vent, ventriculus (stomach)
making only a few turns or loops in its course. It consists of three principal parts, of which the middle part is the true stomach, or ventriculus (Vent) as it is called by insect anatomists. The first part of the tube includes a
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