HIBERNATION. 113 



Table XLIX. — Relation of climate to survival of boll weevils in hibernation — €on. 



Place and year. 



Description. 



Periods of emer- 

 gence. 



Rainfall and tempera- 

 ture, Oct. 1-Mar. 15. 



Rain- 

 fall. 



Abso- 

 lute 

 mini- 

 mum. 



Total 



below 

 32. 



Keatchie, La. 

 1905-6. 



Mansura, Tex. 

 1909-10. 



Calvert, Tex. 

 1906-7. 



Dallas, Tex. 



1906-7. 



Victoria, Tex. 

 1906-7. 



Mansura, La., 

 1908-9. 



18 cages, variety of 

 shelter (1 bare), in- 

 stalled Nov. 18- 

 Dec. 18. 



19 cages, great variety 

 of shelter, Sept. 16- 

 Dec. 14. 



10 cages, variety of 



shelter, Oct. 1-Dec. 



10. 

 10 cages, variety of 



shelter, Oct. 13- 



Dec. 6. 

 10 cages, variety of 



shelter, Oct. 25- 



Nov. 29. 

 19 cages, great variety 



of shelter, Sept. 28- 



Dec. 21. 



Mar. 22-June 2S . 



Feb. 15-.Iune 15 . 

 Mar. 4-July 1 . . . 

 Mar. 1-June 19.. 

 Feb. ;.'«.-. I une 15. 

 Feb. 21-June 29 . 



Inches. 

 18.87 



15.37 

 11.87 

 8.52 

 11.25 



10.41 



"F. 

 21.0 



19.5 

 26.0 

 22.0 

 27.0 

 23.0 



>F. 

 91.0 



151.5 

 47.0 



145.0 



5.0 



81.0 



One of the most striking features of Table XLIX is the disparity 

 between the percentage of survival through the six winters considered. 

 A special effort has been made to discover the factors that cause this 

 disparity. Among those that have been considered are the absolute 

 minimum temperature, the daily accumulated degrees below 32 

 during the hibernation season, the number of times a temperature 

 below 32° was reached, and the rainfall. Contrary to our expecta- 

 tions, it appears that the number of times the temperature descends 

 below 32° has no direct effect. However, there seems to be a direct 

 relation between the absolute minimum temperature and the rainfall, 

 taken together, and the percentage of survival. As the absolute 

 minimum ascends and the rainfall decreases the survival seems to 

 increase. The greatest survival (Mansura, La., 1908-9) was accom- 



{)anied by the third highest minimum temperature and the third 

 owest rainfall during the hibernation season. In the same way the 

 next to the highest survival (Victoria, Tex., 1906-7) was accom- 

 panied by the highest absolute minimum temperature and the fourth 

 lowest rainfall. Conversely, the lowest survival (Tallulah, La., 

 1910-11) was accompanied by the lowest absolute minimum tem- 

 perature and the lowest rainfall. The next to the lowest survival 

 (Dallas, Tex., 1907-8) was accompanied by the third lowest absolute 

 minimum temperature and the highest rainfall. It thus appears that 

 a moderately cold winter, with temperature frequently near the zone 

 of fatal temperatures and excessive precipitation, is very unfavor- 

 able for the weevil, but a winter with little precipitation and a tem- 

 perature within the zone of fatal temperatures is by far the most 

 ratal. Conversely, a winter with temperatures always above 20° and 

 moderate precipitation is the most favorable for the weevil. 



28873°— S. Doc. 305, 62-2 8 



