33 



greatest rainfall is in January at College Station, and probably the 

 largest number usually succumb in that month. 



That the rainfall is probably the most important factor in deter- 

 mining the mortality of the hibernating brood is very apparent upon 

 studying the platted curves for rainfall and temperature for diiferent 

 points where we have made observations as to the abundance of the 

 Aveevil for several years. After a wet winter weevils are fewer, and 

 after an open dry one they are exceedingly abundant. This has never 

 been more strikingly illustrated than last winter, which in southern 

 Texas was unusually dry and open, whereas during the previous win- 

 ter there had been a marked excess of rainfall. As a result, in the 

 spring of 1904 the weevils appeared in enormous numbers and a crop 

 failure resulted, whereas in 1903 this section made a crop in manj^ 

 cases above the average, although this was partially due to weather 

 conditions in summer. A study of the normal mean temperature and 

 rainfall of southwestern, southern, and central Texas shows that 

 undoubtedly the larger mortality in the last section is due to the more 

 unfavorable winter weather. 



Hunter and Hinds have stated that the weevils usually emerge from 

 hibernation after the temperature has been over 60° for some time, and 

 that in 1903 they emerged after it had been at 68° for some time. xVfter 

 studying the available data with the aid of temperature curves, plat- 

 ted for various points where the time of emergence was known, I am 

 convinced that this is approximately correct and that when the mean 

 daily temperature becomes 68° the first weevils commence to emerge. 

 Thus the weevils would nonnally commence to emerge at Victoria 

 about xVj^ril 1 and at College Station April 15. Usually the weevils 

 will commence to emerge ten days earlier in southwestern and coast 

 counties than in central and eastern Texas, and about twenty days 

 earlier than in northern and northwestern counties. 



The weevils do not all emerge at once, however, but continue to 

 appear for from four to six weeks. Usualh^ the greatest number of 

 weevils appear about the time the cotton commences to square, and 

 the beginning of oviposition is but a few days later, as it has been 

 shown by Hunter and Hinds that a female must feed upon the squares 

 before she will commence ovii^osition. After this time very few of 

 the hibernating brood appear. That the time of this maximum 

 emergence, as well as the squaring of the cotton plant with which it 

 seems to be largely coincident, is dependent upon weather conditions 

 may be taken for granted. But what are these conditions? Hunter 

 and Hinds have shown that the average mean temperature at which 

 the weevil is active and reproduces throughout the season is about 

 78° F. Thus it might seem that when the mean daily temperature 

 had become 78° the maximum emergence would take place, but com- 

 25524— No. 52—05 m 3 



