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



peculiar instinct may have arisen, concludes that "the death- 

 feigning instinct of Talorchestia longicornis is an instinct, which, 

 - - - - , has its root in the thigmotactic responses common among 

 other amphipods." 



It is a matter of common observation, that various aquatic 

 insects belonging to different orders manifest the instinct of 

 feigning death when taken out of the water. The instinct crops 

 out among some of the nymphs of the orders Plecoptera, Ephe- 

 merida and Odonata, and again among the Neuroptera, as in 

 the larva of Corydalis and the adults of Sialis. The death feint 

 also occurs among some of the larvae of the aquatic Coleoptera 

 and is developed to an unusual degree in some of the families 

 of the aquatic Hemiptera. Traces of the death feint are found 

 in some of the adults of the families Corisidae and Notonectidae, 

 but it is in the family Nepidae that this instinct reaches its 

 highest development among the adults of this group. Again, 

 in the family Belostomidae, which includes Belostoma flumineum, 

 the form with which we have been working, this instinct is 

 exhibited to a marked degree, while in the closely related forms, 

 Lethocerus americanus and Benacus griseus, also members of 

 this family, this phenomenon can sometimes be induced with the 

 proper manipulations. 



It is agreed generally that all aquatic insects descended from 

 terrestrial forms. It is evident that adaptations for an aquatic 

 existence must have arisen independently amongst insects a 

 number of times, for the families of insects that lead an aquatic 

 life are often only distantly related and belong to different 

 orders. If the instinct of feigning death was not handed down 

 through inheritance from the various terrestrial ancestors to 

 the aquatic representatives that exhibit this phenomenon, it 

 must have arisen independently during their aquatic existence. 



Holmes (13, p. 163) gives the following interpretation of the 

 death feint in Ranatra : "In fact Ranatra very seldom leaves 

 the water of its own accord on account of any sort of induce- 

 ment, 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 peculiari- 

 ties of the organism than an instinct which has been built up 

 by natural selection for the benefit of the species." 



Is there any reason for believing that the instinct of feigning 



