30 



BULLETIN" 173, U. S. DEPARTMENT OF AGRICULTURE. 



greater rainfall, the month of February, 1909, having 4.87 inches 

 precipitation while February of 1910 had only 0.83 of an inch. 



A comparison of the amount of precipitation for the three years 

 1909, 1910, and 1911 (see Table III) shows a large amount for 1909, 



eso 



600 

 S50 

 SOO 

 450 



























































































































































































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350 

 300 

 250 

 200 



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/4 /6 /S 20 22 24 26 2& 2 <4 6 & /O /2 /4 /6 /& 20 22 24 26 2ff 



1 



Fig. 11.— Curve showing emergence of pear thrips at Suisun, Cal., 1910. (Original.) 



which with the low average mean temperature for the two emergence 

 months caused the emergence to be drawn out. The season 1911 

 was very abnormal in the large amount of precipitation, especially 





































































































































































































































































































































































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/O /2 /4 /€ /3 20 22 24 26 2 



9 2-4 € e /O /2 /4 /6 /a 20 2 



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 APR. 



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 J200 

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 /OOO 

 950- 



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700 



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400- 



300- 



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Fig. 12.— Curve showing emergence of pear thrips at San Jose, Cal., 1909. (Original.) 



during the latter part of February and early March, causing a late 

 blossoming season, and holding the thrips back to such an extent 

 that comparatively little injury was caused by the adults. 



