Page:Insects - Their Ways and Means of Living.djvu/141

 AND MEANS OF I_.IVING

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. , 63, 83), but it will be seen that all are merely adaptations of form based on the ordi- nary biting type of mouth appendages. The fossil records of t'he 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 alimen- tary canal, and to live them whatever crushing or masti- canon is necessarv. It is within the alimentary canal, therefore, that the next steps toward the final nutrition of the animal take place. The a]imentary cana] of most insects is a simple tube (Fig. 68), extend'ing either straight through the body, or

FI{I. 68. The alimentary canal of a grasshopper IInt, anterior intestine; dn, anus; Cr, crop; GC, gastric caeca, pouches of the stomach; Hphy, hypopharynx (tongue); Lb, base of labium; Mal, Malpighian tubules; Mlnt, raid-intestine; llth, mouth; Oe, oesophagus; Rect, hind intestine (rectum); SIGI, salivary glands opening by their united ducts at base of hypo- pharynx; I/ent, ventriculus (stomach)

making only a few turns or loops in its course. It con- sists of three principal parts, of which the middle part is the true stomach, or ventriculus (Fent) as it is called by insect anatomists. The first part of the tube includes a

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INSECTS