LIFE-HISTORY OF DRAGON-FLY 231 



first larval skin, and when that difficulty is overcome 

 the special instincts of its kind manifest themselves. 

 From first to last all are carnivorous, but adopt various 

 ways of overcoming their prey. The nymphs of some 

 dragon-flies conceal their body in the mud, under the 

 surface of which they make their way by slow puffs 

 of the tail, and then dart out upon some passing 

 beetle, larva, or worm. Others lie motionless among 

 the weeds, with the colouring of which their own 

 agrees, and spring out from cover upon their prey. 

 A few bolder forms make no concealment, but pace 

 up and down seeking for provender. 



These nymphs are provided with a singular weapon 

 for catching prey. This is the ' mask ' or under-lip, 

 which is greatly elongated and doubled back by a 

 hinge-joint until it almost touches the forelegs. To 

 its free end is hinged a pair of curved opposable teeth, 

 and when the desired prey is yet an arm's length off, 

 this long arm is smartly extended with a sudden jerk, 

 the prey is seized by the teeth, and whipped back 

 into the safe grip of the other jaws. 



After the third or fourth moult, buds of the two pairs 

 of wings appear on the thorax, and grow steadily larger 

 at each stage, the eyes increase in size, and the nymph 

 prepares for its final change. It climbs up a support, 

 fills its tracheae with atmospheric air, and shovels off its 

 investment. The brilliant fly emerges, and in a moment 

 develops all the power of flight it will ever display. 



May-flies. — Among the mazy dancing insects that 

 haunt rivers, some relatives of the dragon-fly are well 



