THE PEAK THRIPS IN CALIFORNIA. 



27 



following close behind. The increase in emergence during the season 

 1909 (fig. 12) and the tapering off in the same year was more gradual 



300 

 275 

 250 

 225 

 200 

 /75 

 J50 

 /25 

 ZOO 

 75 

































































































































































































































































































































































































































































































25 

 O 



































































































/2 /4 /6 /ff 20 22 24 26 2ff 2 4 6 6 /O /2 /4 /6 /& 20 22 24 26 2e 



Fig. 7.— Curve illustrating emergence of adult pear thrips at laboratory, Walnut Creek, Cal., 1909. 



(Original.) 



than during the season 1910 (fig. 13). This difference was most 

 probably influenced during the latter season by the temperature. 



800 

 750 

 700 

 650 

 60O 

 S50 

 500 

 450 

 400 

 350 

 300 

 250 

 200 

 /50 

 /OO 

 50 

 O 



Fig. 8.— Curve showing emergence of pear thrips in cages under trees in field at Walnut Creek, Cal., 



1909. (Original.) 



RELATION OF EMERGENCE TO TEMPERATURE AND RAINFALL. 



The average mean temperature for February and March, 1911, or 

 the two months when practically all of the thrips emerged, was 































































































































































































































































































































































































































































































































































































































































































































































/4 /6 /a 20 22 24 26 £ 



9 2 4 6 S /O /2 /4 /6 /& 20 2 

 Ms4&CH 



2 2. 



'4 26 2\ 



9* 



