104 DRAGONFLIES [CH. IV 



imperceptible approach. The larvae of all species are 

 most difficult to detect; some closely resemble the mud 

 in and on which they live, others are like black water- 

 logged bits of stick, others living among green water-weeds 

 are so coloured as to be practically invisible amidst their 

 natural surroundings. Thus they not only escape the notice 

 of their foes but are able unperceived to approach their 

 prey, which consists of soft-bodied aquatic animals, such 

 as worms, insect larvae, and even tadpoles and small fish. 

 On occasion however they can advance with some speed 

 either by forcible expulsion of a jet of water from the 

 hinder end of the body, or in some species by swimming 

 with the aid of three blades projecting from the posterior 

 extremity. 



The prey is seized by means of the labium (united 

 second maxilla) which is of peculiar construction and is 

 known as the "mask." This contrivance lies under the 

 head and anterior part of the thorax; it is attached, 

 as usual with the labium of insects, below the mouth. 

 When at rest its proximal portion is directed backward 

 and united to the distal portion by an elbow-joint hinge 

 from which the latter projects forward, lying ventral to 

 the proximal portion. Thus the attached base and the 

 free tip are close together at the mouth itself. At the 

 free tip is a pair of sharp movable beaks (the modified 

 labial palps) known as the forceps. When the larva 

 arrives within striking distance of its prey, the " mask " is 

 suddenly shot forward, the elbow-joint straightening out. 

 The forceps seize the animal which is then by a quick 

 return of the " mask " dragged back to the mandibles and 



