BIOLOGY OF THE MEXICAN COTTON BOLL WEEVIL. 5 



(fig. 7). The field hatchery consisted merely of a certain area in 

 the cotton field about 20 feet square. The infested squares were 

 placed in the hatchery beneath the cotton plants in the natural posi- 

 tion of fallen squares. After 15 days from the date of egg puncture 

 the infested squares were placed in small wire-screen hatching cages 

 (fig. 7). The hatching cages were constructed of 16-inesh wire 

 without bottoms and protected the infested squares in such a manner 

 that the squares received about the same amount of sunshine and 

 moisture as under normal field conditions. Maximum and minimum 

 thermometers were installed in the field hatchery (fig. 9). Both in- 

 struments were resting on the soil in order that the exact minimum 

 and maximum temperatures to which the developing weevil was 

 subjected under field conditions might be determined. 



Ten hibernated male and female weevils were used to secure the 

 developmental period of the first generation of weevils on upland 

 cotton. In addition, 10 hibernated female weevils that had not been 

 fertilized were used to determine the effect of nonfertilization after 

 emergence from hibernation on the progeny produced. When the 

 first generation weevils became adults 10 pairs were selected and used 

 for securing the fecundity records on upland, long staple, and sea- 

 island cottons. The fecundity records for the second generation on 

 upland cotton were secured in a like manner. After the 15th of 

 August, however, the weevils had developed so rapidly in the field 

 that it was necessary to discontinue the study of the developmental 

 period of the weevil for each successive generation. 



For securing the effect of the lower fall temperatures on the de- 

 velopmental period of the weevil, upland cotton plants were stripped 

 of all cotton squares and then caged. As soon as the plants grew 

 new squares female weevils were placed in the cages for oviposition 

 purposes. About every 20 days a new series of developmental studies 

 was inaugurated. This process was continued until frost killed the 

 cotton plants in late fall. 



FOOD PLANTS OF THE BOLL WEEVIL. 



Owing to the economic importance of the question as to whether 

 or not the boll weevil can adapt itself to plants other than cotton for 

 food, this phase of the life history has been carefully studied in 

 practically every section of the cotton belt. 



The boll weevil has as regular food plants the cultivated cottons 

 of the United States, Mexico, Cuba, and Central America, and certain 

 wild cottons, including Gossypium davidsoni on the coast of the 

 Gulf of California, and also the so-called wild cotton, Thurberia 

 thespesioides, in Mexico and Arizona. 



