THEIR APPALLING VORACITY. 303 



are jointed to the corners of a flattened and somewhat 

 triangularly-shaped horny plate. When these jaws are 

 closed, they lie so closely against the edge of the horny 

 plate that they can hardly be distinguished from it. 



The triangular plate is jointed below to a narrow plate 

 about equal to it in length, and that again is jointed to 

 the lower portion of the mouth. 



In the illustration, this apparatus is shown as it 

 appears when extended. When closed it is folded under 

 the head, and is not visible from above. It is known to 

 entomologists by the popular name of "mask," because 

 the front of the head is hidden by it as if concealed by 

 a mask. Its appearance when folded may be seen by 

 reference to page 304. 



As soon as the dragon-fly larva has seized its prey, it 

 folds the mask, and by that action brings the victim 

 close to its mouth, so that it can be eaten without having 

 a chance of escape. 



If the reader will examiiie a crab, lobster, or shrimp 

 before eating it, and will fold the joints of its claws, he 

 will find that the claws exactly coincide with the entrance 

 of the mouth, and just the same structure is found in the 

 larva of the dragon-fly. 



The perfect insect does not need the mask, for its 

 movements through the air are so rapid, and its wings 

 so powerful, that no other insect can escape when once 

 the dragon-fly gives chase 



Unlike the moths and butterflies, whose change from 

 the larval to the pupal state is so strongly marked in the 



