INFLUENCE OF CLIMATIC CONDITIONS ESPECIALLY. 43 



that in Group A and a total rainfall for each month averaging 3.75 

 inches, which is 1.92 above the normal, there is a total mortality from 

 all three causes averaging but 19.1 per cent, while that from heat alone 

 averages but 7.1 per cent. A comparison of the mortality from ant 

 work between Groups A and C shows in C a decrease which is very 

 nearly proportional to that found for heat, while the reduction in 

 parasite work is comparatively slight. 



These facts seem to point to the conclusion that other factors than 

 climatic conditions must explain the variations in mortality which 

 are shown in this table. Undoubtedly extreme variations in tempera- 

 ture and rainfall are exceedingly important, but it is obvious that the 

 average variation in these factors does not produce a corresponding 

 variation in the mortality figures, such as might be expected. Evi- 

 dently there are other factors modifying or neutralizing the effect of 

 climatic variations, which if acting alone might produce more consist- 

 ent results. 



INFLUENCE OF CULTURAL CONDITIONS. 



High temperature can affect the weevil stages only after the forms 

 have fallen or been so cut off from vital connection with the plant 

 that the sap flow is stopped and a drying of the form results. The 

 effect upon the weevil stage will then depend upon the conditions of 

 exposure to the heat. If the square or boll remains hanging or dries 

 upon the plant, the temperature in it will not rise as high as if those 

 forms were exposed directly to sunshine upon the surface of the 

 ground. If the square or boll falls to the ground, its position in 

 regard to the shade of the plant will determine largely the degree of 

 exposure to the heat of the sun and, consequently, the probability as to 

 the survival or destruction of an inclosed weevil stage. The direction 

 in which the rows run, and more especially the open distance between 

 plants, will affect the exposure of the fallen forms to the direct action 

 of the sun. The dryness of the surface soil is another factor which 

 will largely affect the drying of the forms and the mortality resulting 

 from heat. The work of the living larvae naturally produces a larger 

 degree of moisture in the infested forms than will be found in those 

 which contain no weevil stage. If the conditions are such as to 

 insure a very rapid and complete drying of the form within a few days 

 after it falls to the ground, there is a strong probability that the 

 weevil stages affected will be destroyed by heat or drying. If climatic 

 or environmental conditions favor the weevil's development until the 

 pupal stage is reached, the condition of the form is then much more 

 favorable for the entrance and attack of the ants. The ants seem 

 to be able to recognize the presence of a living weevil stage within 

 a form and rarely, if ever, enter forms in which the stages have pre- 

 viously been destroyed by heat. If ants destroyed both parasite and 

 weevil stages no evidence of the parasitism might remain. It is 



