THE GRAPE PHYLLOXERA IN CALIFORNIA. 



57 



Table XII. — Comparative monthly average temperatures; inside cages in trench, 

 2 feet below soil surface in laboratory vineyard, and in laboratory cellar, 

 Walnut Creek, Calif. 



Month. 



Two feet 

 below 

 surface. 



In cages 



in 

 trench. 



In labo- 

 ratory 

 cellar. 



1913. 



"F. 



°F. 



159 

 68 

 71 

 71 

 69 

 65 

 56 

 49 



52 

 52 

 56 

 58 

 63 

 68 

 72 

 72 

 66 

 64 

 56 



"F. 









76 



77 



77 



70.5 



64 



53 



54 



51 



58 



62 



65.5 



70 



72.5 



74 



70.5 



66 



58.5 



50.5 



49 



52 



57 



62 



63.5 



71.5 



75.5 



75 



71.5 



66 





August 







68 



October 



63 





59 





56 



1914. 

 January 



55 





55 





58 



April 



59 



May 



62 





65 



July 



67 



August 



69 





67 



October 



63 





58 



December 



54 



1915. 

 January 





54 



February 





55.5 



March 



56.5 



57 



59 



68 



73 



73.5 



69 



64.5 



57 



April 



58 



May 



60 





65 



July 



68 



August 



69 



September 



66 



October. . . 



62 







1 Approximate. 



Examination of Table XII indicates that the cellar temperatures 

 showed the least annual variation and that the average temperatures 

 in the soil for every month, except February, 1914, exceeded the 

 corresponding temperatures in the cages. It is probable, leaving 

 other factors out of consideration, that the accumulated excess of 

 heat in the soil over that in the cages throughout one season would 

 produce an extra generation of phylloxerse, besides prolonging the 

 active development later into the autumn. The summer of 1913 

 was much warmer than that of the year following. This is borne 

 out by the soil temperature comparisons, but does not appear from 

 the cage temperatures. 



To obtain life-history data, the following vines were used : Burger, 

 Muscat, Thompson's Seedless, Mission, Champini, and Grenache. On 

 the Champini the phylloxeree refused to settle, except on fleshy 

 side-rootlets, but on the others they settled at any point. On the 

 Grenache roots, however, several of the inoculations proved unsuc- 

 cessful, the young larvse not settling. On the others, inoculations 

 nearly always proved successful. Inoculations were made by transfer- 

 ring eggs from one root to another with a camel's-hair brush. Since 

 the roots in all cases were vertical, or very nearly so, it happened 



