OUTLINES OF ENTOMOLOGY. 9 



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

 the front upper part (Fig. 2, hj, 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 eheeJcs or Gence. The manner in which these parts are devel- 

 oped varies greatly in different insects. 



The principal appendages or organs of the head are the Mouthy the 

 ^yes and the Antennae. 



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. : jaics for biting and beaks or tubes for 

 sucking. 



The mouth of a biting insect consists of six dis- 

 tinct parts, collectively called TropM. 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 

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



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

 Head of Tiger beetle; a, . , . , i i n i i 



frons; b, epistoma; c, ject to great chauges in shape, and seldom bear much 



labrura; d, eyes: e, man- 

 dibles; /, maxilla;; g, rcseuiblance to the lips of Vertebrates. The upper 



jnaxillary palpi; A, labial 



palpi; i, antennie. qj. principal jaws are termed Mandibles (Fig. 3, eej. 



T?hey are strong and sharply toothed, and are the chief instruments for 

 seizing and tearing the food. 



The lower jaws (Fig. 'S,ffJ are called the Maxillce (sing, maxilla), 

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

 minate in a point. 



Besides these six principal mouth parts, most insects have from 

 one to tliree^ generally two pairs of slender-jointed organs, called Palpi 

 {sing. 2>alpusJ or mouth-feelers. One pair is attached to the lower jaws, 

 and are termed the maxillary palpi (Fig. 3, gj, the other pair, connected 

 with the lower lip, are the labial palpi (Fig. 3, hj. Their office seems to 

 be to aid in the selection of food and to brush impurities from the face 

 and antenuib. 



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 beak, with which the leaves of plants or the skins of ani- 



