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



at the temperature of the atmosphere. The average of the 

 first death feint in ten specimens kept at i8° C. under bright 

 light was 8.7 minutes, while in a dim light and at the same 

 temperature the average was 13 minutes; in the second experi- 

 ment, the specimens were kept at 14°-! 6° C. and now the aver- 

 ages were 13 minutes under a bright light and 20.4 minutes 

 under a dim light. 



That previous subjection to darkness, and a sudden transfer of 

 the insects from this into a bright light has an effect upon the 

 duration of the death feint of Nepa may be seen from the follow- 

 ing experiments. Three lots of specimens were exposed for three 

 hours to the light of a thirty-two candle-power incandescent 

 electric lamp about eighteen inches away, while three other 

 lots were kept in almost total darkness for the same period of 

 time. All were then made to feign in the same intensity of 

 light to which the first three lots had been exposed. The aver- 

 ages of the first death feint in ten specimens used in each experi- 

 ment are as follows: 



Kept in bright Kept in darkness, 

 light throughout then transferred 

 experiment. to bright hght. 



Temperature of atmosphere 18° C. 14.8 minutes. 18° C. 9 minutes. 



18° " 16 " 18° " 6.2 



16° " 10.8 " 16° " 4.7 



Belostoma and Nepa are aroused from their death feint more 

 quickly under a sw^aying light than under a stationary one. 

 Twenty Belostomas w^ere taken from water at 17° C. and caused 

 to feign under a stationary light of a sixteen candle-power 

 incandescent electric lamp, the temperature of the atmosphere 

 being 23° C. Each individual w^as, on an average, about six 

 inches below the light. The time of the first death feint of 

 each specimen under these conditions was as folio w^s: 3, 3, 3, 

 4, 5. 5. 5-5. 6.5, 7- 7, II, 12, 14-5, i7> i7-5, i9, 20, 20.5, 23 and 

 28 minutes, the average being 11.5 minutes. The sixteen candle- 

 power electric lamp was now slowly sw^ayed back and forth at 

 the rate of about one complete oscillation per second above 

 fifteen different Belostomas lying on their backs in a death-feint, 

 the temperature conditions being identical with those in the 

 previous experiment. The following figures indicate the time of 

 the first death feint: .5, i, i, i, i, 1.5, 2, 3, 4, 6, 6, 8, 11, 14.5 

 and 22 minutes, the average being 5.5 minutes. 



