328 Journal of Comparative Neurology and Psychology. 



When Ranatra is compelled to walk on a glass plate while 

 the light is held beneath the body it still carries the head and 

 anterior part of the body high in the air. The head and body 

 are lowered somewhat if the light is placed below and in front 

 of the insect, but not nearly so much so as in a normal specimen. 

 If the light is passed to the rear beneath the glass plate the 

 head and front part of the body are raised up. Lateral head 

 and body movements are performed in the usual way when the 

 light is passed transversely over the posterior part of the body, 

 but as the light is carried forwards these movements become 

 less marked. Similar results are obtained if the light is moved 

 beneath an insect which is placed on a glass plate ; the responses 

 become less evident and precise as the light is carried in front 

 of the body. 



Ranatras with the anterior surface of their eyes blackened 

 over are still able to follow the light when it is in front of them, 

 but their movements are hesitating and their orientation inac- 

 curate. This is a very natural result since the insects must be 

 guided by the light which enters the posterior sides of the eyes. 



10. The Effect of Covenng tJie Posterior Half of the Eyes. 

 Blackening over the posterior surfaces of both eyes produces 

 effects opposite to those observed when the anterior surfaces 

 are blackened over. The insect walks with the anterior part of 

 the body lowered and the head inclined slightly downward. If 

 a light is held behind the insect the head and anterior part of 

 the body are elevated, but not so much so as in a normal indi- 

 vidual. When the light is in front the body is lowered anter- 

 iorly and the head bowed down. The same effects are produc- 

 ed when the Ranatra is placed on a glass plate and the light 

 moved beneath the body. The light is followed very readily 

 when it is kept in front of the body ; if, however, the light is 

 moved to the rear the insect experiences considerable difficulty 

 in orienting itself and frequently travels for some distance direct- 

 ly away from the light before finally turning around. Lateral 

 movements of the head and body are readily brought about 

 when the light is moved from side to side in front of the insect, 

 but they become less pronounced when it is carried further back. 



