OBSERVATIONS ON YOUNG OF RANATRA OUADRI DENT ATA. 163 



water and placed back on the table it feigned for several minutes, 

 the legs giving the same signs of muscular rigidity as before. 

 Several times it came out of its feint and as many times it was 

 caused to resume feigning by dipping it into water and placing it 

 on the table. Contact with a wet camel's hair brush would 

 readily cause it to feign, but a dry brush would produce no feint, 

 or but a very short one. Other experiments gave very similar 

 results. 



It is difficult to understand how the death feint in Ranatra 

 can be of much value to it. While the European Ranatra 

 lincaris has been known to fly to lights at night (a rare occur- 

 rence apparently) I have been unable to obtain any evidence of 

 such a habit in any of our American species. In fact Ranatra very 

 seldom leaves the water of its own accord on account of any sort 

 of inducement, and one is. therefore strongly inclined to believe 

 that the death feint which is manifested only when the insect is 

 in the air is rather an incidental result of certain physiological 

 peculiarities of the organism than an instinct which has been 

 built up by natural selection for the benefit of the species. We 

 must adopt such a view, I think, regarding hypnotism in the 

 higher animals and in man ; for what selective value can it be to 

 a species, such as our own for instance, to possess the capacity 

 of being thrown into the hypnotic state ? The instinct of feign- 

 ing death is of unquestionable service to many forms, and it is 

 possible that in rare instances it may have proven of selective 

 value to Ranatra, but it is open to serious question if the instinct 

 in this form has been evolved because of its importance as a 

 means of protection. 



The strong and at times almost violent positive phototaxis 

 which Ranatra exhibits presents another problem of the same 

 kind. Certain of the most striking features of this reaction are 

 manifested only when the insect is out of water. As a rule 

 Ranatra inhabits more or less shaded retreats among submerged 

 grass or weeds near the water's edge. It is kept in such situa- 

 tions, partly through the direct effect of its positive thigmotaxis, 

 and partly because contact stimuli (as shown in a previous paper) 

 cause it to become negatively phototactic. The positive photo- 

 taxis which appears when the insect is swimming freely in the 



