128 



Texas, undoubtedly tend to carry the weevils in a general northerly and 

 northeasterly direction. The severe equinoxial storms which fre- 

 quently occur in Texas during September, at the very time that weevils 

 seem to be most active in flight, have undoubtedly had a strong effect 

 in carrying the weevils in this same general direction. Thus, after the 

 severe storm which produced the disastrous flood at Galveston on 

 September 8, 1900, it appears that the weevil had been spread north- 

 ward over an area much larger than that covered by its usual annual 

 migration. It seems altogether likel}^ that the very warm, sultry 

 period which almost invariably precedes these severe storms leads the 

 weevils to take wing in large numbers, and the strong winds following 

 these calms exert an influence in carrying the weevils which they 

 have at no other season of the year. 



MIGRATION. 



Two principal periods of extensive voluntary movement on the part 

 of the weevils may be found during the season. The first is when the 

 hibernated weevils leave their winter quarters and go in search of 

 food. Having found food, the movement is mainly controlled b}^ the 

 limitation of the food supply. So long as an abundance of growing 

 tips or of clean squares is at hand, weevils will not travel far, but 

 when the condition of total infestation is reached the period of greatest 

 dissemination is also attained. In an attempt to secure an isolated 

 location free from weevils, a small area was planted in the midst of a 

 rice farm at Victoria, Tex., at a distance of more than a mile from 

 other cotton. Whether the weevils reached this field by flight or by 

 some other means could not be definitely determined, but in some way 

 the field became thoroughly infested during Jul}^. 



In any given field dissemination takes place mainly by the short 

 flights and crawling of the weevils. The search of the female for 

 uninfested squares is the principal factor in their spring and summer 

 movement. This incident also appears to be one of the important 

 factors in producing the annual migration which begins soon after the 

 condition of maximum infestation has been attained. The exact time 

 of beginning this movement seems to depend upon certain favorable 

 climatic conditions accompanying an overstocked condition of the 

 field. 



A number of special agents of the Bureau of Entomology were 

 fully engaged in following the movement and studying the conditions 

 accompanjdng the migration of 1904. A careful study of this move- 

 ment has been made by Mr. W. D. Pierce, who, between August and 

 December, gave his entire attention to the study of the migration of 

 the weevils. From his preliminary report have been taken most of the 

 conclusions embodied in the following paragraphs upon this topic. The 

 observations of a single season furnish insufficient data to allow of 



