238 



ANIMAL AGGREGATIONS 



The Xiphidium have cannibahstic tendencies, which caused sev- 

 eral experiments to be discarded. When Melanoplus were used, they 

 showed greater initial activity but otherwise gave similar results. 



Ethyl alcohol differed from the other vapors used in that the 

 effect on the animals was much more gradual, extended over a 

 longer period of time, and stimulated them to greater activity. 



TABLE XXVI 



Showing the Relative Survival of Groups and Isolated Individuals of the 



Grasshopper Xiphidium, Exposed to Equal Volumes of 27.5 Volume per Cent 



OF Ethylene Gas, August 17, 1928; Barometer 746, Temperature 24° C. 



All were placed in 240 cc. bottles supplied with 66 cc. of the gas. 



* Removed at this time to ordinary air. 



The period of recovery was also longer with this reagent. The dif- 

 ference in recovery between the group and the single individuals 

 was also greater with alcohol than in the case of the other vapors 

 used. 



The outstanding effect noted in the case of insects exposed to 

 HCN was the lack of stimulation when the insects were first ex- 

 posed. Xiphidium in particular remained motionless from the time 

 the gas reached them. Muscular activity could be induced, if at all, 

 only by most vigorous shakings. This would loosen their attach- 

 ment from the bottle or from whatever object to which they might 

 be cHnging. Those that were fully narcotized would fall to the 



