ECONOMIC SIGNIFICANCE OF INVESTIGATION. 95 



II. Tlie amount of control due to the various factors at worTc in any 

 given place should he increased if possible. Parasites can he introduced 

 into new f elds. 



In order to prevent serious injury to cotton, the mortality of the 

 weevil should be above 90 per cent. It has averaged over 57 per cent 

 for four years and has reached almost 100 per cent several times. 



AVhile climatic influences occasionally bring the control above 90 

 per cent, they can not be regulated or in any way directly utilized. 



Although the insect enemies present at a given place may be 

 accomplishing the greatest amount of work possible, the fact remains 

 that if other species of enemies are introduced and become estab- 

 lished the control can be increased. 



Since certain parasites attack the weevil preferably in dry locations 

 and others in wet locations, and since some prefer to attack the 

 infested forms on the plant, while others seek them on the ground, 

 it is possible to select the insect agencies so as to obtain the least 

 amount of lost or duplicated energy. 



III. The parasites and predators which attacTc the holt weevil are 

 native insects, already present in a given territory hefore the weevil 

 arrives. 



The predators, especially ants, will attack almost any kind of 

 insect food. The parasites in nearly all cases are capable of attack- 

 ing almost any kind of weevil breeding in herbs above ground or in 

 fruits. 



The parasites have proven their ability to adjust themselves to 

 the boll weevil by attacking it in its first generation in newly infested 

 territory in instances where the actual sources of the parasites were 

 demonstrable. 



The weeds surrounding the cotton fields contain many weevils 

 which are harboring multitudes of available parasites. These para- 

 sites may be induced to attack the boU weevil by the timely elimina- 

 tion of their native hosts. 



This leads to the recommendation that planters cut the weeds adjoin- 

 ing the cotton fields, along the roadsides, turn rows, and fences ahout the 

 time of the maturing of the crop. 



It also leads to the recommendation that a field adjoining the cotton 

 he used as a pasture or hay field, and that this field he mowed early in 

 the fall. The usual haying will also bring about the same result — 

 namely, the elimination of other plants harboring weevils which 

 attract the parasites needed in the cotton patch. 



It is advisable to have in the vicinity of the cotton field such plants 

 as the dewberry, Croton, Amorpha, cowpeas, etc., which contain other 

 hosts of the boll-weevil parasites. 



