38 BRITISH INSECTS 



drops her eggs at random into a pool or lake, or boldly 

 enters the water in order to lay them upon the sub- 

 merged stems of water-plants, or in the mud at the 

 bottom. The nymphs are quite unlike their parents ; 

 but although those of the various species differ among 

 themselves in details of colour and form, they all pos- 

 sess certain peculiarities which render them unmistak- 

 able. The most characteristic feature is called the 

 "mask" really an elaborate modification of the 

 second maxillae, or labium. The contrivance is des- 

 cribed by Mr. W. J. Lucas as follows : " The base is 

 attached below the mouth ; the hinder half lies under 

 the head and fore-part of the thorax ; there is a joint 

 in the middle, and the fore-part lies under the hinder, 

 bringing the base and tip together close to the mouth." 1 

 This is the position of the mask when at rest. But it 

 can be shot out with great rapidity, in much the same 

 way that a pugilist delivers a "blow from the 

 shoulder." Moreover, the tip of the mask carries a 

 pair of sharp, movable hooks (which are really the 

 modified labial palpi), by means of which the nymph 

 is able to seize any small animal that is unlucky 

 enough to come within range. When a capture has 

 been made, the mask folds back, bringing the victim to 

 the mandibles and first maxillae. A glance at the 

 photograph reproduced on Plate IV. will help the 

 reader to appreciate the manner in which the mask 

 works. 



Dragon-fly nymphs vary in colour from bright green, 

 through yellowish-green to brown, or almost black. 

 Indeed, individuals of the same species often differ 

 greatly in tint ; and it is said that the coloration de- 

 pends almost entirely upon the environment, and is 

 1 " British Dragon-Flies." 



