April, '09] JOURNAL OF ECONOMIC ENTOMOLOGY 165 



In siiiiilar tests with (UtUindm oryza about seventy per cent of the 

 adults were killed in from thirty to forty minutes, and about eighty- 

 five per cent in from forty to fifty minutes. Among 209 adults ex- 

 posed for sixty minutes but five showed subsequent signs of life, and 

 one of these survived for three days but did not feed. This individual 

 showed no sign of life until after having been out of the gas for about 

 thirty-six hours. With this species also all treatments of more than 

 one hour's duration resulted in complete desti'uction of the adults, 

 and also of all immature stages, while nearly all of the latter were 

 killed in the fifty-minute treatments. 



By far the most resistant species thus far tested is Silvaniis suriii- 

 amcnsis, which is associated with Calandra and with Cathartus gemcl- 

 hitus in nearly all of the corn ears examined to date. While some of 

 these adults wei-e killed in treatments of thirty minutes, or even less, 

 an average of but sixteen per cent was killed among over 200 specimens 

 exposed for intervals of between thirty and sixty minutes. Among 

 140 adults exposed for periods ranging between 70 and 100 minutes 

 the death rate was but 55 per cent, but among 200 adults exposed for 

 110 and 120 minutes all were killed. 



The strength of gas actually eft'ective in these experiments was be 

 tween 70 and 80 times that evolved in a treatment using but one pound 

 of the liquid to 1,000 cubic feet of space. As adults in these three 

 species remained active iu this strong gas for from 17 to 30, or even 

 more, minutes, w^e may be excused for doubting the reliability of the 

 statement of the French investigators to the effect that "in an at- 

 mosphere composed of one part of CS2 vapor to 90 parts of air all 

 insects perished in a few seconds. ' ' That strength of gas is not likely 

 to be over one-sixtieth of the strength used in our tests in which the 

 three species mentioned were active for more than twenty minutes on 

 the average. 



In an actual test of the application of the di-sulfid at the rate of two 

 pounds per 1,000 cubic feet at a temperature of 55 to 60 degrees, for 

 a period of twenty-four hours, the adults of both Calandra and Ca- 

 thartus appeared to have been hardly disturbed. There was no indi- 

 cation of any mortality having resulted and when removed from the 

 fumigation chamber at the end of the treatment the adults appeared to 

 be moving and feeding normally. 



Mr. Hinds : I trust that we may have time for some little discus- 

 sion along this line, as we shall certainly appreciate the suggestions 

 that will be brought out thereljy. I had intended to give a few of the 



