10 BULLETIN 344, U. S. DEPARTMENT OF AGRICULTURE. 



vicinity of Tucson the normal emergence in the mountains is scat- 

 tering during the spring and summer months, depending largely 

 upon the frequence of the showers during this period, and that the 

 general emergence is produced by the rains of July and August. 



RELATIVE ATTRACTION OF COTTON AND THURBERIA FOR WEEVILS. 



During the season a number of tests were made to determine the 

 relative powers of cotton and Thurberia for attracting the weevils. 

 Various types of weevils and different foods were used in the different 

 lots but the method of procedure was identical for all. 



Large, weevil-proof screen cages were used. They were placed 

 on bare ground which was kept slightly moist by an irrigation ditch 

 on each side of the row of cages. 



In preparing the cage for the test the Thurberia plant was placed 

 upright in one corner about a foot from the wall of the cage and the 

 cotton plant was placed diagonally opposite. Then the weevils were 

 released on the ground in the center of the cage. Following this, 

 examinations were made frequently to determine the amount of 

 feeding on each plant and the weevils present on each. All weevils 

 found on plants were removed and released in tne center of the cage. 

 Fresh plants were placed in the cages almost every day or often enough 

 to keep green food present at all times. In order to eliminate* the 

 influence of light from any selection the weevils might make, the 

 positions of the plants were reversed daily. 



All weevils were hibernated individuals which were removed from 

 their 1913 pupal cells in Thurberia bolls. The observations may best 

 be divided according to the food of the weevils before these were 

 placed in the test cages. 



WEEVILS NOT FED BEFORE TESTING. 



On the 1st of August 14 males and 14 females removed fiom bolls 

 collected in December, 1913, in the Santa Rita Mountains were 

 placed immediately in a cage with cotton and Thurberia plants 

 bearing neither squares nor bolls. On August 24 plants with squares 

 and bolls were started and continued as the food for the remainder 

 of the experiment. 



Feeding began immediately on both plants and was continued 

 more or less constantly until the close of the experiment on Septem- 

 ber 17. For the first 15 days the feeding was mostly on Thurberia, 

 but after that time cotton was more or less favored. The summary 

 of the observations for the entire period is as follows: 



Cotton attacked records. . 24 



Thurberia attacked do 16 



Weevils on cotton, 3 male, 21 female total. . 24 



Weevils on Thurberia: 3 male, 14 female, 2 of sex not deter- 

 mined total . . 19 



