344 THE ANATOMY OF IXVERTEBRATED ANIMALS. 



modified, and in many ways most instructive forms ; at the 

 same time, it is not too small for convenient dissection. 1 



In this insect the head is vertically elongated, flattened 

 from before backward, and connected by a distinct neck 

 with the prothorax. The antennae are slender, as long as, or 

 rather longer than, the body. Large reniform compound eyes 

 are situated at the sides of the head. The tergal portion of 

 the prothorax (pronotum) is a wide shield, which overlaps the 

 head, in front, and the tergal portion of the mesothorax, or 

 meso?iotum, behind. The legs are strong, and increase in 

 length from the first pair to the last. The abdomen is flat- 

 tened from above downward, and bears a pair of elongated, 

 many-jointed, setose styles (cerci) at its hinder extremity. 



The males differ very considerably from the females. They 

 have two pairs of wings, of which the anterior are brown, and 

 are of a stiff and horny texture. As they serve to cover the 

 posterior wings, they are termed tegmina. When closed, 

 the left overlaps the right, and they extend back as far as 

 the posterior edge of the tergum of the fifth abdominal so- 

 mite. 



The posterior wings, on the contrary, are thin and mem- 

 branous ; and, in a state of rest, are folded longitudinally 

 upon themselves, the folded edge being internal. In this 

 condition they are triangular, the base of the triangle lying 

 close to the posterior edge of the fourth abdominal somite, 

 and the right a little overlapping the left. When forcibly 

 unfolded and made to stand out at right angles to the body, 

 each of these wings is seen to have a nearly straight, thick- 

 ened, anterior edge, while its rounded outer and posterior 

 edges are very thin. The wing is strengthened by radiating 

 thickenings, or nervures, united by delicate transverse ridges ; 

 and, when left to itself, it springs back into its folded state 

 with some force. 



The abdomen of the male is not very broad. The sterna 

 of the abdominal somites are all flattened ; and, to the hind- 

 ermost, tw r o minute un jointed styles are attached, while some 

 singular hooked processes are seen, on close inspection, to 

 protrude between the hindermost tergum and the hindermost 

 sternum. The abdomen of the female is very much broader, 

 especially toward the middle of its length. The hindermost 

 sternum is convex and boat-shaped, and its posterior half is 

 separated along the middle line into two halves, united only 



1 Sfa, for an excellent figure and description, Rolleston, " Forms of Animal 

 Life," p. 199, plate vi. 



