TESTING THE VALUE OF FUMIGATING AGENTS 



3*9 



of surface in the box as compared with that of a very large room. 

 The absorption and surface condensation are increased as the sur- 

 face increases, and a smaller room, of course, has relatively a larger 

 surface than a larger room of the same general shape. 



Hence, as a rule, the fact that mosquitoes are killed in this appa- 

 ratus with a certain amount of fumigant per unit space, under given 

 conditions, will hold for a larger room, under the same conditions. 



_ 410* 3, 



FIG. 9. 



FIG. 7. Section of side showing one cage in position; the cage projects into the lumen of the box 

 and is closed on the outside by a small stopper. 



FIG. 8. Sides of box. 



FIG. 9. One of the wire-gauze cages showing wooden stopper, with hole for introduction of 

 mosquitoes closed by a wooden stopper. 



Conversely, and even more certainly, if a given concentration of 

 fumigant will not kill in the experimental box, in a large space the 

 fumigation, under the same conditions, will be unsuccessful. 



A very interesting and important point has come up in con- 

 nection with this work; namely, the rapidity with which the active 

 fumigating agent is evolved makes a great deal of difference in the 

 efficiency of the fumigation. For example, with the less active 

 fumigants and culicides, as pyrethrum, the difference between com- 

 plete success and complete failure may depend upon the rapidity 

 with which the culicidal substance is evolved as smoke. One pound 

 per 1,000 feet burned in three portions simultaneously is rather more 



