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. 
May . . ■. 
°F. 
°F. 
159 
°F. 
68 
July 
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 
71 
71 
69 
65 
56 
49 
52 
52 
56 
58 
63 
68 
72 
72 
66 
64 
56 
August 
68 
October 
63 
59 
December 
56 
1914. 
January 
55 
February. 
55 
March 
58 
April 
59 
May 
62 
June 
65 
July 
67 
August 
69 
September 
67 
October 
63 
58 
December 
54 
1915. 
54 
February 
55.5 
56.5 
57 
59 
68 
73 
73.5 
69 
64.5 
57 
April 
58 
60 
June 
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 phylloxerse 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 
