44 



which forms frequently an excrescence the size of half a pea upon the 

 inner side of the carpel. An excrescence of this character usually 

 results from an egg puncture, and often from feeding punctures. 



DESTRUCTIVE POWER BY FEEDING. 



A glance at the figures in Table VIII (p. 40) is sufficient to show 

 the great destructive power of the Mexican cotton boll weevil. It 

 may 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 comparison of the 

 figures for males alone with those for females alone or with those for 

 males and females together shows that it is very conservative 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 VARIOUS 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 (Algodon 

 sylvestre). The Peruvian cotton made a remarkably large growth, 

 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 surely 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- 



