HIBERNATION. 113 



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













Rainfall and tempera- 













ture, 



Oct. 1-Mar. 15. 





Description. 



Number 



of 

 weevils. 



Per cent 

 of sur- 

 vival. 



Periods of emer- 

 gence. 







Place and year. 





Abso- 



Total 













Rain- 



lute 



degrees 













fall. 



mini- 

 mum. 



below 

 32. 













Inches. 



°F. 



°F. 



Keatchie, La.. 



18 cages, variety of 



24,700 



2.1 



Mar. 22-June 28 . . 



18.87 



21.0 



91.0 



1905-6. 



shelter (1 bare), in- 

 stalled Nov. 18- 

 Dec. 18. 















Mansura, Tex., 



19 cages, great variety 

 of shelter, Sept. 16- 



22,179 



4.6 



Feb. 15-June 15 . . 



15.37 



19.5 



151.5 



1909-10. 

















Dec. 14. 















Calvert, Tex., 



10 cages, variety of 



19,408 



8.9 



Mar. 4-Jnly 1 



11.87 



26.0 



47.0 



1906-7. 



shelter, Oct. 1-Dec. 

 10. 

 10 cages, variety of 















Dallas, Tex., 



30,864 



10.6 



Mar. 1-June 19 . . . 



8.52 



22.0 



145.0 



1906-7. 



shelter, Oct. 13- 

 Dec. 6. 















Victoria, Tex., 



10 cages, variety of 



22,463 



12.8 



Feb. 28- June 15 . . 



11.25 



27.0 



5.0 



1906-7. 



shelter, Oct. 25- 

 Nov. 29. 















Mansura, La., 



19 cages, great variety 

 of shelter, Sept. 28- 



16,281 



20.0 



Feb. 21-June 29 . . 



10.44 



23.0 



81.0 



1908-9. 

















Dec. 21. 















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- 

 panied by the third highest minimum temperature and the third 

 lowest 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 



