REPRESENTATIVE INSECTS 347 



The next two segments, the mesothorax and metathorax, are made 

 up of sclerites that are intimately associated, and their structure 

 will be discussed together. The mesothorax is joined to the pro- 

 thorax by a membrane which permits of more or less movement. 

 Posteriorly the metathorax is joined immovably with the first ab- 

 dominal segment. The mesothorax and metathorax form a strong, 

 boxlike structure for the support of the wing and leg muscles. Like 

 the prothorax these segments are made up of separate plates, held 

 together by a tough, connecting membrajie. These plates may, how- 

 ever, be divided into three groups: the terguni, or dorsal region; 

 the sternum, or ventral region; and the pleuron, or lateral region. 

 On the dorsal and ventral regions of the body the sutures separat- 

 ing the mesothorax from the metathorax are not very distinct. On 

 the sides of the body, however, there is a very distinct line, or 

 suture, running from the posterior border of the attachment of the 

 second pair of legs toward the dorsal part of the body. This suture 

 divides the mesothorax from the metathorax. The pleura of each 

 of the posterior thoracic segments are again divided by transverse 

 sutures, so that each pleuron consists of two sclerites. 



A pair of legs arises from the lateral and ventral portions of each 

 of the segments of the thorax. Each leg is composed of five parts. 

 The coxa is the first segment and is attached to the thorax by a tough 

 elastic membrane. The next segment, the trochanter, is a very short 

 piece which is hard to distinguish except in the first pair of legs. 

 The femur is the third and largest segment of the leg, and in the 

 case of the metathoracic leg contains the muscles used in jumping. 

 The fourth seg-ment, the tibia, is slender, but about the same length 

 as the femur. The last division of the leg is the tarsus which is made 

 up of three segments, each movable with the other. The segments 

 bear a series of pads, which terminate on the last one in a large 

 suckerlike disc known as the pulvillus. 



There are two pairs of wings. The first pair or wing covers, also 

 called tegmina, is attached to the dorsal region of the mesothorax. 

 They are leathery in texture and do not fold fanlike over the abdo- 

 men. They are strengthened by many veins and cross veins. The 

 second pair of wings is attached to the metathorax. They are mem- 

 branous, with many veins to strengthen them, and fold fajilike over 

 the abdomen when not in use. The metathoracic wings are used 

 in flight. 



