61 



DESTRUCTIVE POWER BY FEEDING. 



A glance at the figures in Tables X and XII (pp. 52 and 60) is suf- 

 ficient to show the great destructive power of the Mexican cotton boll 

 weevil. It ma}" be seen that both in the field and in the laboratory 

 the weevils of the first generation are more active in making punctures 

 than are the hibernated weevils. These generations overlap too far 

 to attribute this difference to the influence of a higher temperature 

 alone, though this factor will account for a large part of it. A com- 

 parison of the figures for males alone with those for females alone or 

 with those for males and females together shows that it is very con- 

 servative to say that males make less than half as many punctures as 

 do females. By the habit of distributing their punctures among a 

 greater number of squares the destructiveness of the females becomes 

 at least five times as great as that of the males. 



This great capacity for destruction has been one of the most evident 

 points in the history of the spread of the weevil, and deeply impressed 

 the entomologists who first studied the insect in Texas. In 1895 Mr. 

 E. A. Schwarz, in writing of the work of the weevil at Beeville, said: 



Each individual specimen possesses an enormous destructive power and is able to 

 destroy hundreds of squares, most of them by simply sticking its beak into them for 

 feeding purposes. 



SUSCEPTIBILITY OF VARIOITS COTTONS. 



An excellent opportunity for observations upon this point was obtained 

 upon the laboratory grounds at Victoria by growing within a small area 

 plants of several varieties of American Upland, Sea Island, Egyptian 

 (Mit Afifi), Peruvian, and Cuban cotton {Algodoii sylmstre). The 

 Peruvian cotton made a remarkably large growth during the first sea- 

 son of growth in 1903 and again from the overwintered roots in 1904, 

 but put out no squares, so that it does not really enter into this com- 

 parison. The Mit Afifi seed was obtained through the courtesy of the 

 Bureau of Plant Industry of this Department from a field grown the 

 preceding season at San Antonio, Tex., in which circumstances led 

 some observers to the opinion that the variety was, to a certain extent, 

 immune. The observations at the laboratory were made by carefully 

 examining the plants, looking into each square, and removing every 

 weevil and infested square found. If there were any distasteful or 

 resistant cotton among these, it would surelj^ be found in this way; 

 and if any variety were especially attractive to the weevils it would 

 be equally apparent. Infested squares being removed, the accident 

 of association or proximity would not determine the location of the 

 weevils found, but all might be considered as having come to the cot- 

 ton with equal opportunities to make their choice of food, and accord- 

 ingly their location has been considered as indicating such choice. 

 The period of observation extends from June to November, except 



