MAY-FLIES AND THEIR NEIGHBOURS 229 



poison-bag, and may therefore be handled with 

 perfect safety, in spite of the formidable and 

 menacing flourish of their tails. 



Fig. 152 shows the larva of one of the smaller 

 and more delicate species of dragon-fly frequently 

 observed flying over and around ponds. In front 

 of the head will be seen a kind of projecting organ 

 called the " mask," which, however, is really its 

 lower jaw. This the larva is able to withdraw and 

 hide beneath its head, in which position the mask 

 lies in wait until some unwary victim is in close 

 proximity, when it suddenly projects forward, and 

 the prey is secured and dragged back to its 

 death. The mask then holds the prey to the 

 true mouth and jaws of the voracious young 

 dragon-fly, much in the fashion of an elephant's 

 trunk. To show what a really formidable weapon 

 this lower jaw or mask is, I have shown it con- 

 siderably magnified at Fig. 153. 



When these insects reach the winged state 

 they become familiar objects, with their handsome 

 metallic colouring and striking speed of flight a 

 wonderful contrast from their early, crawling 

 habits at the muddy bottom of the pond. Their 

 gauzy wings flash in the sunlight as they dart 

 past at a pace that is simply astonishing, con- 

 sidering that it is produced by such delicate 

 muslin-like membranes. Fig. 154 shows a 



