EXPERIMENTS WITH KEROSENE EMULSIONS. 161 



parts kerosene, witli vigorous agitation. When the kerosene disappears, add three 

 parts water, and agitate till a homogeneous emulsion is formed. 



This is more pleasaut to use than soapy solutions, and costs — 



Cents per gallon. 



Standard solution, 50 per cent, kerosene 22 



Dilution A', 2 per cent, kerosene 0. 88 



Dilution B', 1.25 per cent, kerosene 0. 55 



Dilution C, 1 per cent, kerosene 0. 44 



Dilution D', 6.25 per cent, kerosene 0. 225 



Dilution E', 5 per cent, kerosene 0. 22 



The A' and B' were not stable longer than two days ; the remaining dilutions barely 

 one day. 



With the exception of the zamia emulsion, all others were better to use the day of 

 manufacture. 



A mixture called murvite was sent me for trial. It gave similar results to the milk 

 emulsions, when diluted in a corresponding manner. 



Effects upon the Cotton-plant. — These varied greatly, owing to the weather subsequent 

 to the application. 



Emulsions A and B, A', B', IJ to 2 per cent, kerosene, didnot harm the cotton-plant 

 if two cloudy or showery days followed their use. A bright sunny day scorched the 

 tips and edges of the tender leaves badly. 



Emulsions C, D, and E, C, D', E', j)roduced no bad results upon leaves or bolls, 

 and were repeatedly tried, with uniform effects. 



Effects upon Larvce. — 1. I colonized five hundred full-grown larvae upon five cotton- 

 plants, and sprayed them with emulsion A, soap series. In five minutes forty larvae 

 dropped off the plants, trembled, and soon died ; in an hour but one hundred re- 

 mained, none feeding, all hanging from the stems and leaves ; in three hours but eight 

 survived ; the next day all were dead, and the cotton-leaves badly withered. 



2. I prepared forty gallons of solution B', milk, and sprinkled thoroughly one-fourth 

 acre of cotton. The stalks average 7 feet in height, and the worms were very plentiful. 



The next day apparently but one in each hundred was living ; the day following 

 that the difference was quite marked, and at this time, three weeks afterward, the 

 surrounding cotton is defoliated, the sprinkled section remaining vigorous and green. 



3. I colonized one hundred larvae, all ages, on a cotton-plant ; sprayed these with 

 solution C, milk, fifteen worms fell off in twenty minutes ; the remainder quit feed- 

 ing. The next morning but two remained, feebly alive. 



4. One hundred large larvae were colonized and sprayed with solution D', milk. In 

 t«u minutes ten dropped off; in half an hour but thirty-five showed vitality ; in four 

 hours all were dead. 



5. One hundred larvae, small size, were sprayed with the one per cent, kerosene- 

 zamia emulsion ; all died within an hour. 



6. One hundred small larvae sprayed with emulsion B, soap, died in one hour. 



7. Three hundred large larvae were sprayed with solution C, milk. The next day 

 but twelve showed signs of life, and they were evidently moribund. 



8. Three hundred large larvae were sprayed with the zamia emulsion ; all died 

 within four hours, and the repetition of experiment 3 with this solution gave better 

 results than with milk or soap emulsions, the zamia perhaps contributing some toxic 

 action. 



I repeated these experiments with all the emulsions till satisfied that an emulsion 

 of one per cent, kerosene, thoroughly applied, was fatal to all larvae it reached, and 

 harmless to the cotton-plant. 



I noted that as soon as sprinkled the small larvae stopped eating, straightened, and 

 quickly fell to the ground. Older larvae would tremble, evacuate faeces, and hang 

 suspended some time. The anal extremity lived longest. 



The addition of one pound sulphide of potassium to forty gallons of any emulsion 

 seemed to increase the rapidity of its toxic action, but it is objectionable as to smeJl 

 and it« destructive action upon rubber hose. 

 63 CONG 11 



