HIBERNATIOlSr AND DEVELOPMENT OF BOLL WEEVIL. 5 



the daily temperature,'^ it will be seen that the activity of the weevils 

 corresponds ver}^ closely with the rise and fall in temperature. Hunter 

 and Hinds* state that hibernation will commence as the mean average 

 temperature falls to between 55° and 60° F., which our observations 

 of last fail corroborate. They also state that at Victoria hibernation 

 will normally commence about December 1. By referring to figure 2 

 it will be seen that the normal temperature at Victoria drops to 60° at 

 about December 1 and at College Station from November 10 to 15. At 

 Dallas hibernation would be several days earlier and for northeastern 

 Texas generally about November 1 to 10. From the observations 

 available, therefore, it would seem safe to assert that hibernation will 

 usually occur when the mean average temperature drops below 60° F. 



Oct. if. t4a«. NaviJ 



IS M«t| ir Tuaiit. 



yitUU* Hnn>iX 



Fig. 2. — Rainfall and temperature records for College Station and Victoria in 1903-4 compared with 



normals. 



NUMBER OF WEEVILS ENTERING HIBERNATION. 



The number of weevils found in an infested field in the fall at about 

 the time hibernation would normally begin is governed largely by the 

 food supply and is influenced also b}^ the temperature and rainfall 

 during September and October. 



« Concerning the method of plotting the curves it should be stated that the vertical 

 lines upon which the nodes of the curve occur are marked as being the 15th of the 

 month. The mean temperature as given by the Weather Bureau is reported at the 

 end of each month. If we should consider the node of the curve as occurring at 

 the end of the month, we would misrepresent the facts, as during the spring and fall 

 the temperature is on a gradual rise or decline. Consequently if the mean monthly 

 temperature is given for the 15th. of the month, the exact temperature for dates 

 between these nodes can be more correctly ascertained from the curve. This applies 

 also to the figures showing rainfall. 



6 Bui. 45, Div. Ent., U. S. Dept. Agric, p. 81. 



