90 



tion with the plant, still remain hanging thereon by a small strip of 

 bark and gradually become dry and brown upon the plant. Falling is 

 but the natural final consequence of injury or disease (Pi. XV, fig. (38). 

 Whatever its cause, it is brought about in exactly the same way as 

 the shedding of leaves by the plant in the fall, by the formation of an 

 absciss layer of corky tissue cutting off the nbro-vascular bundles sup- 

 plying nourishment to the square. The exact location of the cork 

 area is to be seen at the scar left by every fallen square. 



In 539 cases definitely noted between June and September, 1903, 

 the average time from egg deposition to the falling of the square was 

 9.6 days. For this same period full development required an average 

 of 19 days, so that falling occurred at the middle point in the weevil's 

 development. From a comparison of the time of flaring with that of 

 falling it is seen that the interval between these two points averages 

 about 2.5 days. In late fall the time between oviposition and falling 

 of the squares, as recorded in 21 cases, was found to be about 16 days. 



PERIOD OF OVIPOSITION. 



With the exception of hibernated weevils, it appears that oviposi- 

 tion begins with most females within a week after they begin to feed 

 and continues uninterruptedly until shortly before death. While 

 females frequently deposit their last eggs during the last day of their 

 life, a period of a few days usually intervenes between the cessation 

 of oviposition and death. 



In the case of 52 hibernated females the actual period of oviposition 

 averaged about 18 days, the maximum being fully 92 days. 



In an average made with 21 females of the first generation the 

 actual period was almost 75 clays, the maximum period being 113 days. 



The average period for the females of the first two generations 

 appears to be longer than that for any other. In the third generation 

 the average period for 11 females was 58 days, the maximum being 99 

 days, and in the fifth generation for 5 females the period averaged 18 

 days, with the maximum only 62. 



The approach -of cold weather cuts short the activity of the weevils, 

 which become adult after the middle of August, thereby decreasing 

 the length of their oviposition period. Weevils which pass through 

 the winter actually live longest, but as it must take more or less vital- 

 ity to pass through the long hibernation period their activity in the 

 spring is thereby lessened. 



The weighted, average period of oviposition of the 89 females here 

 mentioned is 55.6 days. 



ORIGINAL HABIT OF DEPOSITING EGGS MOSTLY IN BOLLS. 



In the evolution of the species of insects the abilities to change, to 

 adapt, and to specialize are important factors. Such abilities may be 



