OUTLINES OF ENTOMOLOGY. 455 



the Occiput, which is the back upper part, (Fig. 2, a); the epicranium, 

 the front upper part, (Fig-. 2, b), and the Clypeus, which occupies the 

 space between the epicranium and the mouth. The top of the head is 

 also sometimes called the Vertex; the front, the face or Frons; the 

 sides, the cheeks or Gencv. The manner in which these parts are de- 

 veloped varies greatly in different insects. 



The principal appendages or organs of the head are the Mouth, the 

 Eyes and the Antenna:. 



The mouth presents a variety of forms, being adapted in different 

 insects to the kind of food upon which they subsist, and also to the 

 various offices, besides those of mastication or suction, which are per- 

 formed by it. 



All the variations in structure, however seemingly diverse, are 

 made upon two plans, viz. : jmvs for biting and beaks or tubes for 

 sucking. 



y. o The mouth of a biting insect consists of six dis- 



tinct parts, collectively called Tropin. These parts 

 are the lips — upper and under — and two pairs of 

 strong, horny organs which form the jaws and move 

 from side to side and not up and down like the jaws 

 of the higher animals. The upper lip is called the 

 Lab rum (Fig. 3, c), and the under lip (not shown in 



the illustration), the Labium. These parts are sub- 

 Head of Tiger beetle : • , , , . i jij> i 



a, irons; b, epistoma; ject to great changes in shape, and seldom bear much 



c, labrum; d, eyes; e, 



mandibles; /, maxilla; resemblance to the lips of v ertebrates. The upper 



g, maxillary palpi; h, 



labial palpi; i.antenn.e. or principal jaws are termed Mandibles, (Fig. 3, eej. 

 They are strong and sharply toothed, and are the chief instruments for 

 seizing and tearing the food. 



The lower jaws (Fig. 3, ff) are called the Maxillae (sing, maxilla), 

 and are usually more slender and flexible than the mandibles and termi- 

 nate in a point. 



Besides these six principal mouth parts, most insects have from 

 one to three, generally two pairs of slender jointed organs, called 

 Palpi (sing, palpus) or mouth-feelers. One pair is attached to the 

 lower jaws, and are termed the maxillary palpi (Fig. 3, g), the other 

 pair, connected with the lower lip, are the labial palpi (Fig. 3. h). Their 

 office seems to be to aid in the selection of food and to brush impurities 

 from the face and antenna?. 



The sucking or haustellate insects have the same number of mouth 

 parts, but they are developed on an entirely different plan. In some 

 species, such as the true Bugs, most of the parts are united to form a 

 stiff, jointed beaTc, with which the leaves of plants or the skins of ani- 



