132 



following up closely the good work begun by them, the planter may 

 destroy the stalks so much earlier and thus provide a very efficient 

 assurance for the next year's crop. 



Most planters in the weevil-infested territory are now determined 

 not to poison for the leaf worm in the fall, since with both evils pres- 

 ent, the weevil and the leaf worm, the latter has become a friend rather 

 than an enemy. 



NATURAL CONTROL. 



Doubtles many factors are concerned in the natural control of the 

 boll weevil. The most important ones are probably included among 

 the following topics: 



MECHANICAL CONTROL. 



PILOSITY OF PLANT OBSTRUCTING WEEYIL MOVEMENT. 



In testing the susceptibility of various cottons to weevil injury it 

 it was found that the variety of Egyptian cotton grown (Mit Afifi) was 

 more severely injured than was any other. The next in order were 

 Sea Island and Cuban tree cotton, while the American cottons, repre- 

 sented especially by King's Improved, were less severely injured than 

 were any of the others. It may be noted that the three varieties first 

 mentioned seem more closely related to each other than any of them 

 do to the American. The reason for the evident choice of these cot- 

 tons was carefull}^ sought for, but the only difference which seemed 

 worthy of consideration was found in the varying degree of pilosity 

 upon the stems (PI. XIX, fig. 81). It was found that Egyptian stems 

 were almost perfectly smooth, while Sea Island and Cuban resembled 

 it closely in that respect. Many American cottons, and King's 

 Improved especially, are quite pilose, and it was often noted that upon 

 these weevils showed some slight difficulty in moving about or in 

 climbing the pilose stems of the plant. While this obstacle to weevil 

 activity may seem slight to account for the evident selection of the 

 smoother varieties, no greater difference could be found. As is shown 

 by Table XIY, on page 64, the selection is not due to a difference in 

 taste of the squares. 



In order to test the resistance which varying degrees of pilosity 

 might offer to weevil j)rogress, a number of experiments were made 

 with various stems or fruits. In climbing upon the stems of King 

 plants weevils would catch the spines with the forefeet while pushing 

 themselves upward by means of the tibial spurs of the hind legs placed 

 against the epidermis and between the spines. It was evident that 

 their progress was considerably hindered, and several attempts were 

 often made before a firm foothold was secured. 



Okra pods were next tried, as upon them the spines are very short 

 and stiff'. Weevils climbed these pods with little difficulty. 



The seed pods of Sunset Hibiscus were also tested. The spines 



