42 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 



weevils commonl}^ attack them in their very early stages, and even 

 Avhile they are altogether too small to permit the development of a 

 Aveevil larva. It has been pointed out already l)y Messrs. Hunter 

 and Hinds that the smooth stems and petioles of the Sea Island and 

 ^Egyptian cottons render them much more readily susceptible to 

 injury by the boll weevil than are the Upland types, and if we add 

 to this the disadvantage arising from the later development and the 

 more open involucres the possibility of protecting the long-staple 

 cottons against the Aveevils seems small indeed. 



Instead of being immune to the boll weevil, as at one time hoped, 

 the Egyptian and Sea Island varieties seem to be most lacking in 

 weevil-resisting adaptations, as might, indeed, have been expected in 

 view of the fact that they have been developed in regions to which the 

 weevil has not yet penetrated. The Kidney cottons, which may be 

 looked upon as representing the Sea Island type on the mainland of 

 the American continents, have, as will be seen later, a peculiar 

 feature of protective value. 



ADVANTAGE OF OPEN INVOLUCRES. 



It will be apparent from the facts already recited that the partly 

 closed involucres of the Sea Island and Upland varieties now culti- 

 vated in the United States serve little or no purpose in resisting the 

 boll weevil. On the contrary, they often appear to be an advantage 

 to the insect, serving, as they do, to hide the parasite from its enemies 

 and protect it against the application of insecticides or capture by 

 insectivorous birds.* 



The great variation in the size and shape of the involucre in the 

 different varieties of cotton suggests the practicability of securing 

 sorts with open involucres or with these structures reduced to small 

 dimensions. If the weevils were to be caught by insectivorous birds, 

 like the Cuban oriole, whose weevil-eating habits have been discovered 

 by Mr. E. A. Schwarz, open involucres would be a distinct advantage. 

 It might then be possible also to apply Paris green or other insecti- 

 cides to young buds which are, except in the early spring, the 

 exclusive feeding places of the weevils. 



The practicability of an open involucre will need, however, to be 

 considered from another standpoint. It must be ascertained whether 

 the young buds will bear full exposure. Unlike most of the related 

 plants, the cotton bud is not protected by a calyx. The involucre may 

 be necessary as a substitute, especially in dry climates. In humid 



a Dr. H. J. Webber states that the desirability of open involucres has been 

 aiipreciated and that selections of Upland varieties with a view to the develop- 

 ment of this character have been made. 



