56 



in the immediate vicinity had begun to form squares. These observa- 

 tions were very conclusive, and were sufficient to prove the ineffective- 

 ness of trap rows, even under the most favorable conditions. 



ARE WEEVILS ABX.E TO LOCATE A FOOD SUPPLY AT ANY 

 CONSIDERABLE DISTANCE? 



One would naturally think that insects so highly specialized as to 

 have only one food plant would be provided with some remarkable 

 ability for detecting the location of that plant and for enabling them 

 to reach it from a considerable distance. Experiments were under- 

 taken by Dr. A. W. Morrill to determine whether the boll weevil had 

 any strongly marked sense of the direction of its food supply. 

 Various methods of testing were employed. In experiments 1 to 3 a 

 piece of glass about 20 by 24 inches was allowed to rest upon eight 

 glass tubes placed at the angles and middle of each side and directed 

 toward the center of the glass. The space between the tubes was care- 

 fully filled with cotton. In certain tubes a supply of cotton squares 

 was provided. In others, other green vegetation was placed. The 

 weevils were liberated under the middle of the glass and allowed to 

 move freely in any direction, the object being to see if an}^ consider- 

 able proportion of them would choose the tubes containing squares. 

 In experiments 4, 5, and 6 a cylinder 2 inches in diameter and 18 inches 

 in length was constructed from wire screening. This allowed free 

 circulation of the air and free movement of the weevils in either direc- 

 tion. A suppl}^ of squares was placed outside of one end of the cylinder 

 and various other vegetation at the opposite end. Observations were 

 made to determine the proportions of weevils found nearest the food 

 supply or farthest from it. The various conditions of light and heat 

 were so changed as to determine their influence and equalize the effect 

 upon the movement of the weevils. In the course of these experiments 

 over 250 observations were made upon 100 weevils. A summary of 

 the results shows that 83 weevils were found as near the cotton as they 

 could get, while 90 weevils were as far from it as they could be. One 

 hundred and sixty-one weevils were nearer to the cotton than to the 

 other vegetation, while 193 weevils were nearer to other vegetation 

 than to cotton. In no case did the maximum possible distance from 

 the cotton squares exceed 20 inches, and the minimum varied from 1 

 inch to immediate access to the squares. All weevils were hungry and 

 many starved during the period of observation. At no time was there 

 a general movement in the direction of the food supply. Considering 

 these results it can not be said that these weevils showed a definite 

 sense of the direction of their food supply, or any attraction to it from 

 a distance, even so short as 1 foot. The reactions to light and heat 

 were both positively marked and much more evident than the reaction 

 to food supply. 



