2 BULLETIN 731, U. S. DEPARTMENT OP AGRICULTURE. 



bracts surrounding the cotton square and on to the bud itself. In addi- 

 tion, a considerable portion of the experiments included principally 

 treatments very early in the season before the squares had appeared. 

 At this stage of growth the prime objective was to drive the poison into 

 the terminal bud which forms the tip of the young cotton plant and 

 which is the favorite weevil food before squares are formed. As has 

 been mentioned, however, the results secured from all these attempts 

 to poison the weevil were, generally speaking, very dubious and gave 

 no apparent reason for hope for the successful poisoning of the weevil. 



THE WATER-DRINKING HABIT OF THE WEEVIL AND ITS BEARING ON 



POISONING. 



During the seasons of 1913 and 1914 the writer conducted a nuniDer 

 of biological investigations on the boll weevil from which an intima- 

 tion was obtained of the possibility of utilizing certain newly dis- 

 covered features in an attempt to poison the weevil. It seemed 

 quite obvious that there was no hope of successfully poisoning 

 weevils if full dependence were placed on the amount of poison they 

 would secure in the course of their feeding. These studies, however, 

 demonstrated very clearly the importance of water to the continued 

 existence of the weevil. It was found that under cage conditions 

 they drank water very regularly and it seemed reasonable to assume 

 that under field conditions they would secure this apparently essen- 

 tial moisture by drinking from the rain or dew collected in droplets 

 on the leaves of the cotton plants. With this idea in view, the 

 writer decided to conduct experiments in which the attempt would 

 be made to poison the water which the weevils would drink. 



THE POISONING TESTS OF 1915. 



The first tests of this nature were instituted in 1915 and have been 

 continued to date by the various agents of the Delta Laboratory of 

 the United States Bureau of Entomology under the direction of the 

 writer. The majority of these tests were located in the vicinity of 

 Tallulah, La., which is in typical delta territory and normally subject 

 to an exceedingly heavy degree of weevil injury due to the great 

 humidity and excessive rains which prevail. For the purpose of these 

 experiments of 1915, triplicate series of plats were surveyed on three 

 different plantations near Tallulah. Each of these series consisted 

 of five plats of about one acre each, as nearly uniform as possible in 

 all conditions affecting their production of cotton. In each case the 

 two end plats were given four, five, and six applications of poison, 

 respectively. It was soon evident that this poisoning was exerting 

 a very decided control on the weevils, as the weevil infestation was 

 considerably reduced in the poisoned plats and these plats continued 

 blooming much later in the season than did the adjoining unpoisoned 



