HEX APOD A 31 



have jaws for chewing this kind of food. Among the sucking insects the 

 butterfly merely sips the nectar from flowers, while the mosquito needs a 

 powerful instrument for piercing its victim. In this place the typical 

 form of the mouth-parts as illustrated by the biting insects is described. 

 The various modifications of it presented by the sucking insects are 

 described later, in the discussion of the characters of those insects. 



In the biting insects, the mouth-parts consist typically of an upper 

 lip, the labrum (Fig. 62, 8); an under lip, the labium (Fig. 62, 12); and 

 two pairs of jaws between them. These jaws open sidewise, instead of in 

 a vertical direction, as do the jaws of the higher animals. The jaws of 

 the upper pair are called the mandibles (Fig. 62, 10); the lower pair, the 

 maxilla; (Fig. 62, 11). There may be also within the mouth one or two 

 tongue-like organs, the cpipharynx and hypopharynx (Fig. 62, 13). The 

 epipharynx is attached to the upper wall of the cavity of the mouth, 

 and the hypopharynx to the lower. The position of the hypopharynx is 

 quite analogous, therefore, to that of our tongue. 



The mandibles vary much in form, but usually each consists of a 

 single sclerite. The maxillae of biting insects, on the « 



other hand, are very complicated organs, each com- ; W^*^1 



posed of several scleritcs. Each maxilla bears an appen- ^nH^, /»\' 

 dage consisting of several segments; these appendages f^EU^i0^ 

 are termed the maxillary palpi. In the maxillae of cer- ^fflrg^ 

 tain biting insects, as the grasshoppers and the ground ^H^f 



beetles, there is an appendage usually consisting of two *^ Bp 



segments: this is the galea or outer lobe. In some of Wt~4 



these insects, as the ground-beetles and the tiger-beetles, *& 



the galea is shaped like a plapus, and thus there appear Fre. 63. — Maxilla of 

 to be two pairs of maxillary palpi (Fig. 63). The la- 

 bium is furnished with a pair of jointed appendages; these are the labial 

 palpi (Fig. 62, 12, d). 



The Thorax and its Appendages 



The thorax is the second or intermediate region of the body; it is the 

 region that bears, in the adult insect, the organs of locomotion, the legs, 

 and the wings when they are present. This region is composed of three 

 of the body-segments more or less firmly joined together; the segments 

 are most readily distinguished by the fact that each bears a pair of legs. 

 In winged insects, the wings are borne by the second and third segments. 

 The first segment of the thorax, the one next to the head, is named the 

 prothorax; the second thoracic segment is the mesothorax; and the third, 

 the metathorax. 



The legs. — Each leg consists of the following parts, beginning with 

 the one next to the body (see Fig. 64) : coxa, trochanter, femur, tibia, and 

 tarsus. Each of these parts consists of a single segment except that in 

 certain Hymenoptera the trochanter consists of two segments (Fig. 

 64, t), and in most insects the tarsus consists of several segments. The 

 number of segments of the tarsus usually varies from one to^ five. Fre- 

 quently the first segment of the tarsus is much longer than either of the 

 other segments, and it may also differ greatly in form from them ; under 

 such circumstances it is sometimes designated the metatarsus (Fig. 64). 

 The last segment of the tarsus usually bears one or two claws. 



