134 



the formation. The percentage of weevil larvoB found in these bolls 

 was exceedingl3^ small, averaging onl}^ about 5 per cent. The number 

 was so small that no definite conclusions could be drawn as to the 

 effect of the gelatin formation upon the development of larvae, unless 

 it be that the small percentage of larvae found in itself shows that the 

 formation was decidedly effective in destrojdng either eggs or very 

 young larvae, thus reducing greatly the number of weevils produced. 

 Where larvae were found it appeared that the percentage of iiportality 

 was somewhat greater in bolls from early maturing cotton than in the 

 bolls from late varieties of cotton. 



An examination of nearl}^ 1,000 bolls, partly of King and partl}^ of 

 late cotton, in the autumn of 1903 showed a ver}^ decided difference 

 in the percentage of dead larvae found in the two varieties tested. In 

 the native cotton the percentage of dead larvae amounted to about 20, 

 while in King over 41 per cent were dead. In this examination large 

 numbers of larvae were found. The results of the examinations in 

 these two seasons are strikingly different, and as yet no explanation 

 of the difference can be given. 



GELATIN FORMATIOX IN SQUAHES. 



Experiments thus far made have failed to show that either the per- 

 centage of gelatin formation or the injurious effect of this formation 

 upon weevil development can be changed by the application of vari- 

 ous fertilizers or by any special treatment given the plant. Nitrate 

 of soda and acid phosphate, alone and in combination, were the fertil- 

 izers used in the several tests made. 



Comparative examinations indicated that a somewhat larger propor- 

 tion of the squares attacked form gelatin in the case of early maturing 

 varieties than with late native varieties of cotton; as in the bolls in 

 the autumn of 1901 a large percentage of squares having a gelatinous 

 formation failed to show any trace of weevil development, though 

 external indications showed that the squares had received egg punc- 

 tures. Gelatin formation has often been found to begin before the 

 hatching of the egg^ and apparently large numbers of young larvae die 

 when they hatch into this gelatinous environment. 



This ph3^siological reaction becomes, therefore, an important factor 

 in the resistance of the plant to weevil attack, and from present indi- 

 cations it appears that if a trul}^ resistant variety of cotton is ever 

 produced its development will be based upon this factor. 



CLIMATIC CONTROL. 



Three principal factors affect the development, spread, and destruc- 

 tiveness of the boll weevil — temperature, precipitation, and food sup- 

 ply. So perfectly has the weevil become adapted to its single food 

 plant that it is a ver}^ noticeable fact that the climatic conditions which 

 are most favorable to the growth of the plant are most favorable also 



