120 THE MEXICAN COTTON-BOLL WEEVIL. 



Although the grand total of the examinations shows a higher mor- 

 tality due to fallen squares than to hanging squares, it is noticeable 

 that the mortality in hanging squares is greater in Arkansas, Louisi- 

 ana, southwestern, central, northeastern, and north-central Texas, 

 and less in Mississippi, Oklahoma, and southern and eastern Texas. 



As shown in Table LVIII, the highest mortality in fallen squares is 

 67.68 per cent in southern Texas and the lowest 28.06 per cent in 

 southwestern Texas. In hanging squares the highest mortality is 

 67.13 per cent in north-central Texas and the lowest, 7.40 per cent, in 

 eastern Texas. 



Climatic control is highest in fallen squares in north-central Texas, 

 at 43.99 per cent, and lowest in Louisiana, at 13.11 per cent, while 

 in hanging squares it reaches 24.04 per cent only in central Texas and 

 is as low as 3.70 per cent in eastern Texas. 



Predatory control in fallen squares is highest in southern Texas, 

 at 27.43 per cent, and lowest in Mississippi, at 9.88 per cent, while in 

 hanging squares its highest average is 19.75 per cent in central Texas 

 and its lowest no per cent in Oklahoma. 



Parasitic control in fallen squares is highest in Mississippi, at 14.69 



Eer cent, and lowest in eastern Texas, at 1.07 per cent. On the other 

 and, in hanging squares it is highest in north-central Texas, with 

 43.12 per cent, and lowest in eastern Texas, with 2.96 per cent. 



In fallen squares it is generally the case that over half of the mor- 

 tality is due to climate, but in Louisiana, Mississippi, Oklahoma, and 

 southwestern Texas insect control is greater than climatic. In 

 hanging squares the insect control is invariably greater than climatic 

 control, and in Mississippi, Oklahoma, and southwestern and north- 

 central Texas parasitic control alone is greater than the climatic plus 

 the predatory control. It was shown in the table comparing the total 

 mortality in all classes of forms (Table LVII) that the weighted 

 average mortality due to insects was 25.77 per cent, as against 24.45 

 per cent due to climate. All of this evidence is cited to show that in 

 reality the insect enemies produce a very large proportion of the mor- 

 tality of the boll weevil and should therefore be encouraged in every 

 way possible. Of course, it is evident that climatic control is even 

 superior, because of the influences it brings to bear upon every phase 

 of the weevil's existence. 



Regional comparisons such as have been made above are of the 

 greatest importance in determining what factors in natural control 

 need to be given the greatest encouragement by cultural expedients 

 or otherwise. 



CLIMATIC CONTROL. 



From almost every viewpoint the climatic control of the boll weevil 

 is the most important which this insect experiences. The weevil 

 reacts to a multitude of conditions of temperature and humidity. 

 The time of entrance into hibernation, the length of the hibernation 

 period, the time of emergence from hibernation, the length of the 

 various immature stages, the rate of oviposition, and even the pro- 

 portion of sexes are profoundly affected by these agencies. In many 

 cases their effects are not direct. They may affect the weevil indi- 

 rectly through the cotton plant. For example, drought may interfere 

 with the fruiting of the cotton plant and thus deprive the weevils of 

 food. 



