FORM, GROWTH, AND CHANGE 41 



(p) is imjointed. The labium (Fig. 22 D) is wide and flattened 

 with a broad mentum (m) which carries a median plate (ml] 

 in some cases clearly composed of paired elements (perhaps 

 both galeae and laciniae) fused together and a pair of 

 curiously-modified palps, each with two segments (Fig. 22 

 C //, mlti), the basal of which is exceedingly broad. 



The dragon-fly's thorax is strangely modified, the pleural 

 areas of the segments are extensive, so that the body is deep 

 in proportion to its width, and strongly oblique so that the 

 sternal region bearing the legs is thrown forwards towards the 

 head, and the tergal region where the wings are inserted 

 reaches backwards towards the abdomen (Fig. 21). The 

 prothorax is distinct, while the mesothorax and metathorax 

 are somewhat closely united together. The legs are strong 

 though slender, the thighs and shins armed with rows of sharp 

 spines closely arranged ; as the legs can all be held under 

 the head and beneath the mouth, they form an efficient fly-trap 

 for the capture of the small insects that form the dragon-fly's 

 prey. Each foot, as in the grasshopper, has three segments, 

 the terminal one bearing two claws. Unsuitable for walking 

 on the ground, the dragon-fly's legs are admirably adapted 

 for clinging and climbing on plants. The wings are firm and 

 glassy in texture, those of the two pairs closely alike both in 

 form and in their very complex and characteristic nervuration. 

 Dragon-flies are insects with great powers of flight, and the 

 wing musculature is very strong, the muscles for depressing 

 or raising the wings being connected by means of firm tendons 

 to specially-developed sclerites attached to the wing-bases. 



The abdomen is elongate and usually slender, though in 

 one well-known group of dragon-flies (the Libellulinae) it is 

 comparatively broad. The male has, on the second and third 

 abdominal segments, a remarkable and complex armature for 

 pairing, an arrangement found in no other group of insects. 

 The female has an ovipositor composed of three pairs of out- 

 growths on the eighth and ninth abdominal segments corres- 

 ponding to those of the grasshopper. This ovipositor is 

 well developed in those dragon-flies that cut slits in water- 

 plants wherein to lay their eggs, but in large sections of the 

 order the eggs are simply dropped into water and the ovipositor 

 is in a reduced or degenerate condition. At the hinder end 



