April, '19] RICKER: GRASSHOPPER BAITS 199 



rain and wind, with considerable thunder and Hghtning. The rain 

 ceased about 4.30 a. m. and the apphcation was made at 5 a. m. At 

 that time the temperature was 61° F. and the humidity 96 per cent. 

 The average temperature for the five days following the application 

 was 69.34° F. compared to a monthly average of 74.85° F. The aver- 

 age humidity for the period was 77.2 per cent compared to the monthly 

 average of 73.93 per cent. The daily average atmometer reading for 

 the period was 9.66 cc. compared to an average for the month of 24.58 

 cc. The application covered about 20 acres, five of which were in 

 tobacco. About one third of the tobacco had been so severely injured 

 that only the stalks and stems remained. At the end of the two days 

 following the application the mortality was found to have reached as 

 high as 90 to 95 per cent. At the end of the five-day period it had 

 increased to from 95 to 98 per cent. The dead hoppers averaged 

 from 135 dead to a square yard in the pasture and stubble, to 51 to the 

 square yard in the tobacco. Practically no live hoppers could be 

 found. 



It was also noticed that whenever an application was made on a 

 hazy or cloudy morning, which cleared either late in the morning or 

 early afternoon, that a quick and highly efficient kill was obtained. 



One very unusual result was noted in a successful control where a 

 shower came on while the application was being made, and which was 

 followed that night by a heavy rain. Ordinarily one would expect 

 but a very slight kill under such conditions. At the end of two days 

 not more than three or four dead hoppers could be found to a square 

 yard anywhere in the treated area. At the end of five days conditions 

 were practically the same. On the eleventh day the writer, in passing 

 through the field, noticed that dead hoppers were much more abundant 

 than when previously examined. A careful examination showed 

 approximately 20 dead hoppers to the square yard over the entire 

 treated area, which in this experiment covered about 60 acres. Com- 

 pared to the original infestation, there were at least 85 per cent of the 

 insects dead. 



Comparative Value of Different Arsenicals 



Paris green was the popular poison in use at Janesville and conse- 

 quently when poison bait was recommended or used as a control, Paris 

 green was used. However, when the writer helped make an applica- 

 tion he often used crude arsenious oxide, for at least part of the applica- 

 tion. On some 34 control experiments Paris green was used 12 times^ 

 crude arsenious oxide 18 times, and calcium arsenate 4 times. Where- 

 ever crude arsenious oxide was used side by side in a direct comparison 

 with Paris green, as was the case in six experiments, in which applica- 



