4 BULLETIN 10&8, U. S. DEPARTMENT OF AGRICULTURE. 



one of these streams bounds or sections a property. The houses 

 thus located are in the higher and more open portions of the plan- 

 tation and usually at maximum distance from the timbered and 

 swamp areas on either side. It is evident that such location of the 

 habitations is favorable in respect to distance from the breeding 

 areas of Anopheles mosquitoes, with the exception of those mosqui- 

 toes that originate in the bayou itself. 



PROBLEM OF ANOPHELES CONTROL IN THE REGION. 



Of course complete drainage of surface water is the logical method 

 of Anopheles control where that method applies, but in the absence 

 of a drainage outlet, and in the presence of surface water favor- 

 able for Anopheles breeding throughout the season, other means 

 must be given local consideration. In any consideration of drain- 

 age in the Delta it is necessary to note that the streams of this 

 region flow away from the river, that the slope of the land is 

 from the bayou bank toward the swamp areas on either side, and 

 that the fall in the bed of the bayou averages less than a foot to the 

 mile. Under these conditions the question of drainage involves an 

 extensive area; it is not a matter which the plantation owners can 

 consider individually. 



The idea of impounding water to suppress mosquito breeding is 

 rather foreign to the general conception of the effect of impounded 

 water upon mosquito production. The relation which impounded 

 water will bear to mosquito production depends altogether upon the 

 conditions under which the work is done and the changes brought 

 about in comparison to the natural conditions. In the question of 

 impounding water in a bayou we must consider the natural character 

 of such a stream and the relation of the stream to the roadways of the 

 plantation and the habitations of the people who cultivate the land. 

 The bayou bank is the logical location for the houses of the tenants 

 and it is important to control the breeding of Anopheles in this near- 

 by source. The bayou under natural conditions favors mosquito pro- 

 duction but under impounded conditions does not. The change in 

 conditions is brought about by the preliminary clearing and by the 

 provision for a permanent water level sufficiently high to suppress 

 the growth of aquatic vegetation. Following these operations, the 

 maintenance of a clean margin is all important. 



BAYOU WALNUT AND THE ANOPHELES SURVEY. 



The work of the Bureau of Entomology was done in a section of 

 Bayou Walnut which quarters the southwest portion of Hecla plan- 

 tation. This bayou runs a very irregular course from a point slightly 

 north of Milikens Bend on the Mississippi Kiver to Bayou Round- 

 away, joining the latter stream southwest of Tallulah. From the 



