132 THE MEXICAN COTTON-BOLL WEEVIL. 



to have been uninfested. Five more squares were submerged for 31 

 hours. These produced two normal adults, and one pupa died in the 

 process of molting after removal from the square. Death was prob- 

 ably caused in the last case by drying; one square was found to contain 

 a dead pupa, and one was not infested. To test the possibility of its 

 living, should the square be penetrated by water, a naked pupa was 

 submerged for six hours, but in spite of this unusual treatment it pro- 

 duced a normal adult. Numerous larva? removed from squares and 

 placed in water pupated in one or two days, and several pupae 

 remained alive, though floating for several days in water before they 

 transformed into adults. 



In the case of squares floating normally it is evident that they 

 might remain in water for several days without injury to the weevil 

 within. Very slight wetting of the cell takes place, even under the 

 extreme conditions of submergence. The effect of a brief flood 

 would not, therefore, be at all injurious. As adults float as readily 

 as do squares, they may also be carried long distances, and, further- 

 more, they are able to crawl out of the water upon any bushes, weeds, 

 or rubbish which they touch. Even when floating for several days 

 continuously they are able to live and may be carried directly to 

 new fields. The floating of adults and infested squares explains the 

 appearance of weevils in great numbers along high-water lines 

 immediately after a flood. 



Field observations were made to supplement the laboratory experi- 

 ments recorded in the preceding paragraphs. In July, 1904, many 

 fields in the vicinity of Victoria, Tex., were partially and some wholty 

 submerged. This condition lasted for several days. Examination 

 made after the recession of the water showed that many fallen 

 squares which had been in the water for some time contained unin- 

 jured larva? and pupa?. Naturally, eggs and larva? found in squares 

 upon the plants, even though under water for some time, escaped 

 unharmed. Weevils were working normally upon the plants. No 

 diminution in their numbers could be seen, and it was apparent that 

 the overflow caused no check either to the development of the imma- 

 ture stages or to the activity of the adults. 



PLANT CONTROL. 



While climate is the foremost factor in the control of the boll 

 weevil and also of the behavior of the cotton plant, there are certain 

 kinds of control which the plant itself exerts. One of the most 

 important of these is proliferation, which will be discussed in the fol- 

 lowing paragraphs. 



PROLIFERATION. 



Early in the investigation of the boll weevil it was noticed that the 

 immature stages and sometimes even the adults are frequently 

 killed by a form of reaction of the plant known as proliferation. 1 It 

 appears that this property of the plant might be emphasized by 

 breeders. For this reason special studies were conducted in 1905 



1 Dr. O. F. Cook, of the Bureau of Plant Industry, has published a number of papers in which references 

 are made to proliferation. The reader is referred to these papers, which are included in the bibliography 

 at the end of this bulletin, for a full discussion of the botanical aspects of the phenomenon. 



