INSECTS 



them to pursue, and which they capture by means of 

 grasping hooks on the end of their extraordinarily long 

 underlip (Fig. 134 A), which can be shot out in front of 

 the head (B). The great swampy lakes of Paleozoic times 

 must have furnished an ideal habitat for dragonflies, and 



it is probable that the most ancient 

 dragonflies known had a structure 

 and habits not very different from 

 those of modern species. 



Another very common insect of 

 the present time, which appears 

 likewise to be a direct descendant 

 of Paleozoic ancestors, is the may- 

 fly (Fig. 60). The young mayflies 

 (Fig. 61) also live in the water, and 

 are provided with gills for aquatic" 

 breathing, having the form of flaps 

 or filaments situated in a row along 

 each side of the body. The adults 

 (Fig. 60) are very delicate insects 

 with four gauzy wings, and a pair 

 of long threadlike tails projecting 

 from the rear end of the body. At 

 the time of their transformation 

 they often issue in great swarms 

 from the water, and they are par- 

 ticularly attracted to strong lights. 

 For this reason large numbers of them come to the cities 

 at night, and in the morning they may be seen sitting 

 about on walls and windows, where they find themselves 

 in a situation totally strange to their native habits and 

 instincts. The mayflies do not fold their wings horizon- 

 tally, but when at rest bring them together vertically 

 over the back (Fig. 60). In this respect they, too, appear 

 to preserve a character of their Paleozoic ancestors; 

 though it must be observed that the highly evolved 

 modern butterflies close their wings in the same fashion. 



[96] 



Fig. 59. A young dragon- 

 fly, an aquatic creature 

 that leaves the water only 

 when ready to transform 

 into the adult (fig. 58) 



