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THE POPULAR SCIENCE MONTHLY. 



the hood, prolonging the front, and running down in front of the 

 mouth. The head is generally articulated with the prothorax by 

 a fine ligament, which leaves it more or less freedom of motion in 

 all directions. 



The mouth of insects is arranged to masticate, lick, or suck 

 food. The buccal parts are of course fitted to their purpose, but 

 the type to which all should be referred is the masticatory appa- 

 ratus, which, by repeated applications to functions foreign to its 



Fig. 6. Pabts of which the Body of a Cole- 

 opter is composed, c, head ; th', first 

 ring; of the thorax (prothorax) ; th", sec- 

 ond ring of the thorax (mesothorax) ; th'", 

 third ring of the thorax (inetathorax) ; a, 

 abdomen. 



Fig. 7. Mouth of a Masticating Insect. 

 Is, labrum ; md, mandibles ; mx, jaws and 

 maxillary palpi ; h, lower lip and labial 

 palpi. 



primary destination, has been insensibly modified and at last 

 transformed, according to circumstances, into a licking or suck- 

 ing apparatus. The buccal organs of masticating insects move 

 laterally, after the manner of scissors, while the jaws of verte- 

 brates work up and down, like pincers. 



When we examine the mouth of the masticating insect, we find 

 in it parts in the order indicated in Fig. 7. First is an upper lip, 

 or labrum, Is; second, a pair of upper jaws, or mandibles, md; 

 third, a pair of lower jaws furnished with maxillary palpi, mx ; 

 and fourth, a pair of labial palpi supported by a lower lip, h, 

 which is itself attached to the border of the buccal cavity forming 

 the chin. The articulated mandibles on the cheeks are strong 

 pincers, which sometimes attain a very considerable development. 

 They are often dentated on their inner border. 



The lower jaws are composed of several pieces. Their inner 

 lobe is frequently furnished with a brush of silky threads, and 

 sometimes ends in a little mobile tooth, such as may be remarked 

 among the Cicindelce, (Coleoptera). The outer lobe is often articu- 

 lated in the same way as the palpi. The insect may then be re- 

 garded as having two pairs of maxillary palpi. 



