90 THE MEXICAN COTTON-BOLL WEEVIL. 



was in a belt coincident with a strip known locally as the "dogwood 

 ridge." 



The winter of 1910-1 1 also w T as unfavorable to the w r eevil. It began 

 with a sudden freeze on October 29, wiiich extended over almost the 

 entire infested region and destroyed the food supply. Severe cold 

 weather in January also contributed to the control. Examinations 

 made in June and August, 1911, demonstrated that the w T eevil was in 

 the lowest average condition numerically that it had ever reached. 

 It was completely exterminated in the northern portion of the Texas 

 and Oklahoma black prairie, but w r est of this was a region which 

 escaped the first frost, and wiiere the w T eevils occurred in more or less 

 normal numbers. 



The defoliation by the leaf worm was so widespread that a condition 

 of maximum infestation was reached with much smaller numbers of 

 weevils than usual, and the scarcity of proper food supply forced a 

 phenomenal advance along the Mississippi Kiver toward Tennessee. 



In Texas and Oklahoma there were some gains made in the lost 

 territory, but even with these gains 24,000 square miles of territory 

 were not reinfested. The northern limit of cotton production in 

 western Arkansas w r as reached, and the line of infestation stopped 

 only about 10 miles short of the southwestern corner of Tennessee. 

 Great gains were made in northern Mississippi, and w r estern Alabama 

 and Florida became invaded for the first time. 



HIBERNATION FLIGHT. 



The fall dispersion movement continues more or less regularly 

 until frosts occur and mark the beginning of the hibernation period. 

 Thus, in many cases the fall dispersion is a flight into winter quarters. 

 However, a period of feeding seems to be necessary for successful 

 hibernation. Therefore, few of the dispersing weevils which are 

 forced into hibernation by cold weather survive. Those that do 

 survive seem to be supplied from a distinct movement into hibernation 

 quarters at the end of the season. The most striking observation 

 on this point was made by Mr. J. D. Mitchell in the winter of 1906. 

 Although there had been no lowering of the temperature, he found 

 on entering the cotton fields on November 18 a very restless activity 

 among the weevils. Adults were observed upon the squares with 

 their wings open and flew at the least disturbance. He observed 

 many hundreds of weevils rising into the air and disappearing. The 

 weather was warm and pleasant, and there appeared no reason at the 

 time for this flight, winch continued for about two days. In a few 

 days the temperature became decidedly lower, and Mr. Mitchell was 

 able to find only a very few weevils remaining in the fields. This 

 note is of special interest in connection with the observations on cli- 

 matic control, which will be discussed later. 



OTHER FORMS OF NATURAL SPREAD. 



Heavy windstorms, hurricanes, and cyclones are powerful agents 

 in the spread of the weevil. It is believed that the great storm of 

 September S, 1900, in Texas, carried the infestation northward many 

 miles. As has been stated, the storms of about May 7, 1910, in Missis- 

 sippi, were instrumental in causing a considerable increase of the 

 infested territory in that State. 



