78 OUT OF DOORS. 



appendage to the mouth, is developed into a powerful 

 instrument of apprehension. It is greatly elongated, 

 being fully one-fourth as long as the entire insect. It 

 increases gradually in width from its junction with the 

 head to the end, which is armed with two short but 

 sharp jaws, curved and toothed in their interior edges. 

 It is furnished with two hinges, one at the junction of 

 the ' mask,' as it is called, and the other about half of 

 its length, so that it can lie flat against the breast, the 

 hinge descending as far as the base of the first pair of 

 legs, and the jaws lying exactly over the lower jaws of 

 the mouth. It is called the mask because its broad 

 end lies over the mouth and face of the insect so as to 

 conceal them. When the larva sees some creature 

 which it wishes to eat, it propels itself quietly beneath 

 its unsuspecting prey, turns over on its back, and, with 

 a sharp darting movement, seizes the unfortunate insect, 

 and holds it against the true jaws, by which it is soon 

 devoured. 



The voracity of this larva is extraordinary, and it 

 seems capable of continually eating. As for my own 

 specimens, they were so voracious that at last I took 

 them out of the aquarium and put them into a vessel 

 of their own, supplying them with flies and other 

 insects. I found that, although they would eat blue- 

 bottles in lack of other food, they never seemed to like 

 them, although they would readily eat as many house- 

 flies as could be supplied to them. One day, thinking 

 that the formidable larva of the water-beetle was quite 



