THE PEAR THKIPS IN CALIFORNIA. 



25 



of being very early, as the first thrips were found in the field on 

 January 29 and in the emergence cages February 1; but the heavy 

 rains following in February and March caused it to be very back- 

 ward, so that thrips were not common in the field until March 14, 

 which was about the time of the true maximum emergence. 



In Contra Costa County during the season of 1909 the maximum 

 number of thrips emerged in cages, which were put in the ground 

 in the yard at the laboratory, from February 23 to March 4. (See 



Fig. 5. — Type of soil cage used for soil samples in obtaining emergence records 

 of the pear thrips at San Jose, Oal. (Original.) 



Table VI and fig. 7.) In cages placed under trees (see fig. 6) in the 

 field the thrips emerged in maximum numbers from February 26 

 to March 12 (see Table V and fig. 8). During the spring of 1910 the 

 first thrips found to emerge in the cages at the laboratory were out 

 on February 18 (see Table VI and fig. 9) and in the field cages on 

 February 21, reaching a greater daily emergence by March 1, and 

 continuing to emerge in considerable numbers until March 15, the 

 maximum emergence being March 7 (see Table V and fig. 10). By 

 comparing figures 7 and 8, which show the emergence records for 



73390°— Bull. 173— IS 4 



