DISCUSSION OF BOLL WEEVIL. 129 



the leaf -worm as beneficial. This is especially true in the alluvial 

 soils, where the foliage is excessive in amount. Here, anything that 

 will let in the light late in the season assists in the ripening of the cot- 

 ton, and is therefore beneficial. 



Mr. Morgan said that there was another aspect of the relation be- 

 tween these two insects that seemed of importance. The leaf -worm, 

 by stripping the plants of foliage, deprives the boll weevil of food, 

 and thus causes it to migrate farther. In this way, the spread of the 

 insect was undoubtedly extended last year. If we let the leaf-worm 

 come into our fields early, we hasten the spread of the weevil towards 

 the more important cotton regions farther east. If, however, the 

 caterpillar recommendation prevails, it seems important to emphasize 

 the possible value of the caterpillar in connection with weevil suppres- 

 sion only when it (the caterpillar) appears late in the season ^other- 

 wise careless planters might accept this recommendation as an excuse 

 for neglect when caterpillar damage came too early and threatened 

 the cotton crop. 



Mr. Hinds called attention to the fact that when the leaf -worm is 

 ahead of the weevil it actually delays the spread of the latter by 

 rendering the conditions for its survival so precarious that few of 

 those migrating live. 



Mr. Newell said that we had commonly supposed that the existence 

 of a defoliated area would tend to make the weevil go farther in its 

 migratory flight in search of suitable food, and that, vice versa, an 

 area in which the cotton was rank and luxuriant and not defoliated 

 would have the effect of discouraging the weevil from extending its 

 flight farther. With this in mind, it seemed not improbable that the 

 migratory flight of 1905 would be limited by the Red River Valley. 

 In reality, however, the weevils crossed the Red River Valley into 

 the hills to the eastward, and the area covered by the 1905 migra- 

 tions was as great as that covered by those of 1904. 



Mr. Hunter said that he had in mind especially, in discussing the 

 probable spread of the boll weevil, the work of Professor Webster on 

 the chinch bug. He could not see why the two insects were not likely 

 to follow the same route. 



Mr. Webster stated that he could see no good reason why the brill 

 weevil should not follow the same trend of diffusion as had other 

 insects that had spread from eastern Mexico into the United States, 

 as, for illustration, the chinch bug. He thought that the trend of 

 diffusion would be more rapid to the eastward than to the northward, 

 but there were several facts to be taken into consideration. At 

 present the spread was with the trend of commerce in cotton; after 

 the Mississippi River had been crossed, the spread of the pest would 

 be against this trend of commerce, which would be presumably to- 

 31024— No. 60—06 m 9 



