148 E. MELVILLE DuPORTE 



effect of reducing the duration of the feints. While the number 

 of successive feints was higher than was the case under the 

 effect of chloroform it was not as high as was obtained under 

 normal laboratory conditions. Only one individual feigned 

 sufficiently often to be killed by the fumes of the ether. 



TABLE IV 



Shows the Average Duration in Seconds of the First Feint in a 



Large Number of Individuals Under Normal Conditions and 



Under the Influence of Physical and Chemical Agents 



The Nature of the Death Feigning Instinct. The death feigning 

 instinct occurs in many widely different animals, even among 

 certain birds and mammals. The advantage of the instinct to 

 the possessor is a doubtful one. In the case of insects and 

 other animals, the color of which resembles that of the natural 

 environment, the power of feigning death is an additional safe- 

 guard against the prying eyes of the enemy. But in many 

 cases the death feint is not only useless but may be positively 

 injurious, so that the instinct cannot wholly be regarded as an 

 advantageous adaptation, nor can its origin and subsequent 

 evolution be accounted for on the grounds of usefulness to 

 its possessor. 



The instinct undoubtedly has its roots in some fundamental 

 physico-chemical reaction of zooplasm. Holmes believes that 

 in the amphipods the death feigning instinct has its foundation 

 in the thigmotactic reactions common among these animals. 

 The Severins also advance the theory that the reaction in Nepa 

 and Belostoma is thigmotactic in nature. The results obtained 

 with Tychius picirostris, in the writer's opinion, corroborate the 

 theory that the physico-chemical reaction responsible for the 

 manifestation of the death feint is of the same nature as that 

 which calls forth the thigmotactic response of many insects 

 and other animals and also of such plants as the Mimosas and 

 other " sensitive plants." It must be borne in mind, however, 

 that the statement that the death feigning instinct is thigmo- 



