62 



THE STUDY OF INSECTS. 



appendages are termed the maxillary palpi. In the maxillae 

 of certain biting insects, as the grasshoppers and the ground 

 beetles, there is an appendage usually consisting of two 

 segments : this is the galea (ga'le-a) or outer lobe. In some 

 of these insects, as the ground-beetles and the tiger- 

 beetles, the galea is shaped like a palpus, and thus there 

 appears to be two pairs of maxillary palpi (Fig. 76). 

 The labium is furnished with a pair of jointed appendages ; 

 these are the labial palpi (Fig. 75, 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. Jj): 



coxa, trochanter, femur, tibia, 

 and tarsus. Each of these 

 parts consists of a single seg- 

 ment except that in certain 

 Hymenoptera the trochanter 

 consists of two segments (Fig. 

 jy, t), and in most insects the 

 tarsus consists of several seg- 

 ments. The number of seg. 

 ments of the tarsus varies from 

 one to six ; the most common number is five. Frequently 

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



a b c 



Fig. 77.— Legs of insects : a. Wasp ; b. 

 Ichneumon-fly; c, Bee ; /, trochanter; 

 fit, metatarsus. 



