LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 



Bureau of Plant Industry, 



Office of the Chief, 

 Washington, D. C, September 26, 1905. 



Sir : I have the honor to transmit herewith a report on " Weevil- 

 Resisting Adaptations of the Cotton Plant," and to recommend it 

 for publication as Bulletin No. 88 of this Bureau. This report has 

 been prepared by Mr. O. F. Cook, bionomist in charge of investiga- 

 tions in the agricultural economy of tropical and subtropical plants. 

 It contains an account of his observations and experiments which 

 show that some of the varieties of the cotton plant have definite 

 weevil-resisting characters. The establishment of these facts opens 

 new and unexpected lines of approach to cultural solutions of the 

 weevil problem. 



The investigation of cotton referred to in this report was begun 

 in March, 1904, through the Laboratory of Plant Breeding, there 

 having been set aside for it from the emergency cotton boll weevil 

 appropriation a part of the funds which had been devoted to the 

 breeding of weevil-resistant cotton. The existence of a field culture 

 of cotton in the presence of the boll weevil had been ascertained by t 

 Mr. Cook during a visit to Guatemala in 1902, and it was hoped that 

 the immunity of the cotton might prove to be due to some weevil- 

 resistant quality. 



The first result of detailed observations was the discovery of the 

 weevil-eating kelep or so-called Guatemalan ant, which has been 

 made the subject of previous reports through the Bureau of Ento- 

 mology. It now appears that the usefulness of this insect is not 

 limited to the boll weevils which it catches and kills. By making a 

 regular field culture of cotton possible in the presence of the boll 

 weevil it has contributed in an important manner to the development 

 of the weevil-resisting characters here described. The cotton plant, 

 it seems, has been greatly modified in protecting itself against the 

 ravages of its insect enemy. Xot only has it attracted the kelep to 

 its service and developed other means of defense which are more 



