234 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



portance than any others need only be mentioned as an illustration of 

 this class. The general difficulty is that we cannot tell what their 

 effect may be until it becomes too late to take proper advantage of 

 the conditions which the}^ produce. 



Natural enemies, both predaceous and parasitic, may also be valu- 

 able allies in the fight and every advantage possible should be taken 

 of them, but it is simply folly for the cotton planter to sit idly by 

 trusting nature to do all of the control work for him. However, it 

 is certain that we would have a much more hopeless task in attempt- 

 ing control Avithout the help of these natural factors and we may 

 well stud}'' object lessons of the strongest kind, which nature fre- 

 quently gives us as practical effects which man may himself, in some 

 measure, reproduce. 



Methods of Direct and Indirect Combat. — Naturally, through 

 their general api)]icability to similar problems, the first recourse of 

 the entomologist and of the planter as well is to insecticides. It is 

 sufficient to say that "hosts" of these, both promising and otherwise, 

 have been carefully tested and invariably found practically useless 

 in fighting the weevil. The most promising and also widely tested of 

 them all is Paris Green dusted on the young i)lants at intervals be- 

 ginning before squai-es form, but its use has })r()ven so constantly dis- 

 appointing when applied that it has been practically abandoned by 

 entomologists and by most ])lanters. 



The real reason for failure with Paris Green applies with equal 

 force to all other arsenicals and to contact insecticides as well. Owing 

 to the practical impossibility of applying it to those ])artially pro- 

 tected places where the weevils normally feed, onlj' from one third 

 to one half, on the average, of the adult weevils on the plants at the 

 time of the treatment can be killed. The very long period of emer- 

 gence from hibernation makes the number of weevils on the plants at 

 one time but a very small fraction of the entire number which may 

 survive and attack the crop. This renders frequent treatments neces- 

 sary and their effectiveness is only partial at best. The immature 

 stages cannot be reached by any insecticide, as they are surrounded 

 constantly by several layers of vegetable tissue, and to penetrate that 

 would require a power in the insecticide that would be fatal to the 

 plant. Repeated applications of dry Paris Green (and of other in- 

 secticides as well) will often do more damage to the crop through its 

 harmful effect upon the growth of the plant than would the weevils 

 if allowed to do their worst. 



No method of applying any efficient fumigant has been found ap- 

 plicable to a field crop like cotton. Small-scale experiments with the 

 leading fumigants have indicated that none of them could be de- 



