6o AGRICULTURAL EXPERIMENT STATION. 



demonstrated that the mosquito is particularly susceptive to the fumes of nar- 

 cotic herbs. In the primary stage of my experiments I employed a mixture 

 of 6 different vegetable powders, 2 of which were of a narcotic nature, the re- 

 maining 4 being employed as smoke carriers and aromatics. I came to the 

 conclusion, however, that a mixture of that kind for practical use would be 

 too complicated or difficult to obtain ; therefore I set to work to root out those 

 ingredients which were viseless or those which could readily be dispensed with. 

 For all of my experiments I employed a glass case (21 x 20 x 10 inches) in the 

 dual capacity of execution box and test chamber to compare the combusti- 

 bility of the different powders. 



First Experiment: Test of Coiiibitstibility — Each of the vegetable powders 

 was taken and mixed with one-third its weight of saltpetre to facilitate the 

 process of combustion. They were separately ignited, and in this test pow- 

 dered Foenugreek seeds was thrown out as useless, leaving five ingredients 

 for the Second Experiment. 



Weight and Density of Smoke — The same quantity of the five remaining 

 ingredients was taken and mixed. with Saltpetre, as in experiment number i. 

 The weight of smoke of the separate five ingredients was about equivalent. 

 The smoke rose to the top of the chamber rather rapidly, being propelled by 

 the explosion-like ignition of the combustion agent; from there, meeting with 

 an obstruction in the shape of the top of the chamber, the smoke distributed 

 itself uniformly, the only exception being Chenopodium, which had a dense, 

 heavy smoke, due to moisture present. Under normal conditions, that is, 

 when the powder is thoroughly dry, the weight of smoke was equivalent to 

 the others, but a little more dense, which I ascribe to the presence of fatty 

 oils. This experiment only proved the adaptabilit}'^ of the powders as fumi- 

 gators, but not the effectiveness as an insecticide. 



Test as to the Effectiveness of the Pozvdcrs as Eumiferous Insecticides — 

 This was by far the most interesting experiment of the three, the outcome of 

 which caused me to modify the composition of my fumigating powder. Twelve 

 live hibernating mosquitoes were captured, placed in the experimental cham- 

 ber and subjected to the fumes of po.wder number i (Pyrethrum). I waited, 

 two hours for the fumes to take effect, and upon opening the cabinet the in- 

 sects were found none the worse for their experience. They appeared to be 

 somewhat weak, but readily revived upon admission of fresh air to the cham- 

 ber. I killed these insects in a cyanide jar, as they were unfit for future ex- 

 periments. A fresh supply of the insects was confined in the chamber and 

 subjected to the fumes of powder number 2 (Chenopodium). It was noticed 

 that the insects relinquished their hold on the sides and top of the chamber 

 in 10 minutes, falling on their backs stupefied. In this condition they remained 

 for almost one and one-half hours, but quickly revived wlien fresh air was 

 admitted to the chamber. I decided to omit pow"der number 3 (Nutmeg) in 

 these experiments, not alone because of its high commercial value, but because 

 it served only as an aromatic in the composition. Powder number 4 (Hyo- 

 scyamus leaves) next was ignited and about a dozen insects were subjected 

 to its narcotic fumes. The insects were found stupefied in about eight min- 

 utes. The chamber was kept closed for a period of two hours and all the 

 insects died during that time. 



Powder number 5 {Stramonium leaves) was next in turn. This drug 

 proved to have the same effect as powder number 4, but appeared to be 

 more powerful. The insects that were exposed to its fumes dropped to the 

 bottom of the chamber in from four to five minutes and died in one hour 

 in the closed chamber. These series of experiments proved to me con- 

 clusively that the dried and pulverized leaves of Datura stramonium are, so 

 far, the best adapted to destroy the hibernating mosquito. The fumes are 

 practically harmless to the human organism and, even if there was the 

 slightest effect upon the system, a fatality ought not to occur, as there 

 is no necessity for the operator to remain in the room where the powder 

 is burning. Cellars number 11 and 13 were both subjected to the fumes 

 of stramonium in my investigation, and from 80 to 90 per cent, of the in- 

 sects were killed. Cellar number 6 was treated twice, the first time with the 



