LAET^ OF WATEE-FLIES. 251 



this extremity there are articulated two olaw-like pieces, which 

 open and close at the will of the insect. When this apparatus 

 is in repose, the first joint folds backward under the head of 

 the creature, the second folds forward, and the claw-like pieces, 

 when placed together, form a kind of cup, which covers a 

 portion (more or less, according to species) of the lower part 

 of the face. So closely does this prehensile arrangement pack 

 away, that its presence may easily escape unnoticed. When 

 the animal wishes to seize any prey, it creeps very stealthily 

 and slowly up to its victim, and when near enough shoots out 

 with great rapidity the apparatus just described, seizes the 

 victim with the claw-like part (a. Fig. 155), and drags it, firmly 

 held, to within a convenient distance of its mouth. The limb 

 is used so quickly and surely that one is reminded, while seeing 

 it in operation, of the tongue of the frog, ah-eady referred to 

 in Chapter VII. The creature does not often miss its mai'k. 

 This " mask " has little or no lateral' movement. 



The larvae and pupse of Dragon-flies are not only very in- 

 teresting in their manner of obtaining food, but they are, if 

 possible, even more interesting in their method of respiration. 

 Those, however, which belong to the two sub-families, the 

 ^schnidce and the Libellulides, differ somewhat in their 

 breathing arrangements from those of the Agrionides. The 

 former have at the extremity of their bodies five spines, two 

 being much smaller than the other three. These spines, which 

 can be opened and closed at the will of the animals, surround 

 an opening which leads into the interior of the body, in which 

 the tracheal, or air, tubes are situated. Through this orifice, 

 thus guarded, these insects can draw water into the latter part 

 of their bodies, and then having, by means of the respiratory 

 apparatus which is placed there, extracted aU the oxygen it 

 contained, they discharge (6, Fig. 155) it through the same 

 opening by which it entered. This water is generally expelled 

 gently, but occasionally with great rapidity and force. When 

 the latter is the case, the animals are driven through the water 

 with considerable speed. Indeed, this forcible expulsion of 

 water is the only way by which these creatures can travel with 

 anything like celerity from place to place. Under such influence 



