WORK OF LOUISIANA CROP PEST COMMISSION. 121 



plished by destruction of the cotton })lants in the area involved and 

 by systematic hand picking of adult Aveevils and infested squares 

 from trap jDlants. 



Early in August of lOO-t, the special field agents of the Bureau of 

 Entomology who were employed in Louisiana under the immediate 

 personal supervision of Prof. H. A. Morgan, then entomologist of 

 the crop pest commission, discovered boll weevils generally distrib- 

 uted in cotton fields where a few days before careful inspections 

 had revealed none at all. Their numbers, as well as their occurrence 

 in cotton fields several miles distant from the two original colonies, 

 precluded all possibility of their being individuals whicli had 

 escaped destruction at the time of extermination of these colonies. 

 In all of the infested fields Professor Morgan and his assistants 

 found only adult weeAnls, eggs, and very young larva?, showing (hat 

 the arrival of the adult weevils in fields many miles apart had been 

 practically simultaneous. 



Only one explanation of this phenomenon presented itself, and that 

 was that these weevils had migrated from the infested cotton fields 

 of Texas. Further examinations of cotton fields during the summer 

 and autumn months of 1904, b}^ Professor Morgan and the special 

 field agents of the Bureau of Entomology, established the existence 

 of a marked and clearly defined migratory movement of the weevil 

 into new territory. This migratory habit of the weevil, which had 

 previously been unknown and evidently unsuspected— as it is not 

 mentioned in any of the writings upon this insect prior to that time — 

 entirely revolutionized the methods to be employed in retarding its 

 progress into new territory. The attempt to eradicate infestations 

 within the territory covered by the yearly migrations became not only 

 impracticable but impossible, as fields in which the cotton might be 

 destroyed in the work of exterminating the insect would become rein- 

 fested from surrounding territory immediately upon cotton being 

 again planted therein. 



The migratory movement of 1901, while most marked and exten- 

 sive during the latter part of August, continued with greater or less 

 volume until frost, the weevil's movements during the latter part of 

 the season being more or less continuous and hardly distinguishable 

 as distinct migrations. The territory gained by the weevil during 

 the month of August more than equaled in area all of the territory 

 gained by it during September, October, and November. The area 

 infested by the weevil in December, 1904, is seen in figure 3. 



The w^inter of 1904-5 was one of the most severe that Louisiana 

 has seen for many years, the temperature being much lower than 

 usual and the rainfall much in excess of normal for the winter 

 months. 



