26 HENRY H. P. SEVERIN AND HARRY C. SEVERIN 



first, depending upon the direction in which the lamp is moved 

 with reference to the body of the insect. Soon, however, the 

 movements increase in vigor, the animal performing the move- 

 ments with machine-like regularity and precision. These head 

 movements may be given without any other apparent move- 

 ments of the body or limbs. If the light is continually moved 

 over the long axis of the body, the insect, when it comes out of 

 the death feint, usually turns at right angles to the path that 

 the light is swaying in and runs away. If, while the aquatic 

 bug is running away, the light is again moved back and forth 

 over the long axis of the body, the insect changes its direction 

 almost immediately by turning ninety degrees as before, and 

 continues on its new path. In this way Nepa may be forced 

 to change the direction in which it is moving again and again. 

 If the light is kept stationary, on the other hand, in the center 

 of a circle of feigning Nepas lying on their ventral surface, some 

 facing the light and others turned away from it, in almost every 

 instance will the former turn about and run directly away from 

 it, while the latter will, when they come out of the death feint, 

 run away without turning. Oftentimes when the bugs are thus 

 running away from the light, they can be brought to a stand- 

 still by suddenly placing the light directly before them. With 

 the aid of a light alone, the animal can be forced to go in any 

 direction, and even in a circle by holding the light to one side 

 and a little in front of the creature. From these experiments 

 it is seen that Nepa is decidedly negatively phototactic to the 

 light of a thirty-two or sixteen candle-power incandescent light 

 immediately after the aquatic hemipteron comes out of its 

 feint. 



With Belostoma, however, but few specimens give the lateral 

 and vertical head movements alone in response to the light rays 

 previous to coming out of the death feint. By moving the 

 electric lamp back and forth laterally over the body of some 

 individuals, the head is turned so that its dorsal surface is at 

 right angles to the direction of the light rays, as in Nepa; but 

 if the light is swayed lengthwise over the body, vertical move- 

 ments of the head and prothorax combined are given. When 

 the light is passing from the posterior to the anterior region of 

 the insect, the head accompanied by the prothorax is lowered; 

 if the light is now passed backward, the head and prothorax 



