THE GRAPE PHYLLOXERA IN CALIFORNIA. 



49 



generation eggs, laid May 6 to 8, 1912, under an average temperature 

 of 63° F., incubated in an average of 10.7 days. 



The results shown in Table VII were obtained during 1911 and 

 are in part a complement of those shown in Table VI : 



Table VII. — Incubation records of the eggs of the grape phylloxera, Walnut 



Creek, Calif., ID 11. 





Environment. 



Average 

 tempera- 

 ture. 



Month of 

 incubation. 



Number 

 of eggs. 



Egg stage. 



Group 

 No. 



Average. 



Maxi- 

 mum. 



Mini- 

 mum. 



1 





"F. 



57 

 60 

 65 

 52 

 62 



April 



43 

 177 

 352 



16 



15.14 

 11.03 

 9.07 

 15.09 

 10.66 



18 

 15 

 12 

 18 

 14 



13 



2 



do 



9 



3 



do 



June 



November . . 



8 



4 



do 



15 



5 



In darkness, laboratory drawer. . . 



May- June... 



323 



9 



The eggs of the first four groups in the preceding table were 

 exposed, to light on a shelf in the laboratory, and those of group 5 

 were incubated in a drawer in the laboratory. Both lots were sub- 

 jected to a very abnormal fluctuation of temperature, this fluctuation 

 in some cases reaching 20° F. daily. 



In 1912, 1913, and 1915 some additional incubation records were 

 obtained, and Table VIII indicates the relations between tempera- 

 ture, environment, and incubation to cover the four years, 1911, 1912, 

 1913, and 1915. 



Table VIII. — Relation between incubation, temperature, and environment in the 

 egg deposition of the grape phylloxera, Walnut Creek, Calif., 1911-1913 and 

 1915. 



Lot 

 No. 



Year. 



Number 

 of eggs. 



Average 

 daily 



tempera- 

 ture. 



Incuba- 

 tion. 



Remarks on environment. 



1 



1911 



16 



13 



26 



43 



17 



177 



16 



49 



38 



26 



48 



28 



889 



10 



1,797 



969 



286 



352 



13 



20 



22 



22 



62 



21 



55 



61 



38 



°F. 

 52 

 55 

 56.6 

 57 

 59 

 60 

 60.5 

 61 



61.3 

 63 

 63 



63.8 

 64 

 64 



64.5 

 64.6 

 65 

 65 

 65 

 67 

 67.3 

 68 

 68 

 68.5 

 70 

 70.3 

 72 



Days. 



15.09 



20.50 



1 19. 60 



15.14 



15.50 



11.03 



15.40 



13.60 



15.50 



10.70 



15.50 



11.00 



10.80 



13.30 



10.20 



11.70 



10.29 



9.07 



9.40 



9.65 



8.80 



9.00 



2 7. 00 



7.60 



8.90 



8.40 



8.70 





2 



1915 



Cellar. 



3 



1913 



Do. 



4 



1911 



Exposed to light. 

 Cellar. 



5 



1915 



6 



1911 



Exposed to light 

 Cellar. 



7 



1915 



8 



1911 



Do. 



9 



1913 



Do. 



10 



1912 



Do. 



11 



1913 



Do. 



12 



1915 



Do. 



13 



1911 



Do. 



14 



1911 



Do. 



15 



1911 



Do. 



16 



1911 



Do. 



17 



.1911 





18 



1911 



Exposed to light. 

 Cellar. 



19 



1915 



20 



1913 



Do. 



21 



1915 



Do. 



22 



1913 



Do. 



23 



1915 



Do. 



C4 



1915 



Do. 



25 



1912 





26 



1913 



Do. 



27 



1913 



Do. 









1 Maximum, 27 days. 

 1900°— 21 4 



2 Minimum , 5 days. 



