BUREAU OF ENTOMOLOGY. 233 



gathered so that varietal characteristics may be correlated with con- 

 ditions in the different localities, thus permittin^]^ the designation of 

 certain varieties as best for each type of conditions. 



Hibernation studies were continued to determine whether the 

 ability of the weevil to withstand cold is increasing and to settle 

 related questions. In this connection regular surveys have been 

 instituted with a view to the development of a system of predicting 

 the extent of weevil emergence each spring. A number of so-called 

 weevil remedies were tested at the request of the inventors and all 

 found worthless. A number of mechanical collectors of weevils also 

 were tested and found to be of little or no value. 



A cotton-insect laboratory was established at Thomasville, Ga., in 

 cooperation with the Georgia State Board of Entomology, for the 

 study of the various insects that attack the cotton plant in that sec- 

 tion. This project is of special importance on account of tlie diffi- 

 culties in producing sea-island cotton w^ith the boll weevil present. 

 Another study dealt with the role insects play in the transrnission of 

 cotton diseases. The experiments have shown very definitely that 

 insects are agents in the transmission of certain cotton diseases, and 

 this throws considerable light on the control of these diseases. 



A laboratory was established in the Imperial Valley in California 

 for the investigation of cotton pests, several of which threaten to 

 assume important proportions. 



As in other years, the advance of the weevil was determined, and 

 a map was issued in September. 1916, showing the new territory 

 invaded. 



Tobacco insects. — The investigations relating to tobacco .insects at 

 Clarksville, Tenn., have been confined principally to the tobacco 

 hornworms, the mosaic disease, the tobacco beetle, tobacco cutworms, 

 and miscellaneous insects. 



Field experiments and observations upon remedies for the control 

 of tobacco hornworms were conducted in 11 counties in Kentucky, 3 

 in Tennessee, 2 in Virginia, and 2 in North Carolina. In all, 156 

 experiments with arsenate of lead were made by agents of this 

 bureau, and records of 244 applications of arsenate of lead and Paris 

 green by the farmers were obtained. It was found that the farmers 

 were obtaining practically twice as good results with arsenate of 

 lead, which in many cases they had applied for the first time, as 

 with Paris green, which they had been using for years. The records 

 showed also that results obtained by the farmers were not as good 

 as those obtained from applications made by agents of the bureau. 

 On large tobacco a 4-pound application of arsenate of lead has been 

 found to be sufficient, unless a considerable number of eggs are pres- 

 ent, in Avhich case it is necessary to apply 5 pounds in order to keep 

 the tobacco free of worms for a week or ten days. It was deter- 

 mined, further, that on account of the small spread of the tobacco 

 plants in the more eastern States an application of 3 to 4 pounds 

 will be as effective in certain regions of Virginia and North Carolina 

 as one of 4 to 5 pounds in Tennessee and Kentucky. 



Further improvements in machinery for the application of arsenate 

 of lead have been made, as the results of suggestions by agents of the 

 bureau. 



