56 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



in the Santa Clara Valley, namely, the Landon, Bogen, Sorosis, and 

 Hume orchards. The cages each contained a solid block of earth 

 17 by 17 inches square, representing a surface area of 2 square feet 

 and a depth of 18 inches, below which thrips have never been found. 

 These cages were removed from under prune and pear trees in the 

 several orchards, brought to the laboratory yard, and again em- 

 bedded in the ground to their usual depth and covered with a special 

 cage. A daily record was made of the thrips issuing from each 

 cage. 



Table I. — Records of emergence from soil of adult pear thrips from four orchards in the 

 Santa Clara Valley, California, spring of 1909. 





Number of thrips in four cages. 



Total. 



Date. 



Number of thrips in four cages. 





Date. 



From 



From 



From 



From 



From 



From 



From 



From 



Total. 





Lan- 



Bogen 



Sorosis 



Hume 







Lan- 



Bogen 



Sorosis 



Hume 







don or- 



or- 



or- 



or- 







don or- 



or- 



or- 



or- 







chard. 



chard. 



chard. 



chard. 







chard. 



chard. 



chard. 



chard. 





1909. 













1909. 













Feb. 15 



18 















18 



Mar. 11 



13 



47 



128 



310 



498 



16 























12 



12 



62 



81 



183 



338 



17 



51 











1 



52 



13 



18 



101 



87 



207 



313 



18 



176 



8 



4 



4 



192 



14 



1 



53 



70 



124 



248 



19 



160 



14 



4 



14 



192 



15 



3 



71 



76 



129 



279 



20 



126 



17 



12 



14 



169 



16 



1 



59 



74 



125 



259 



21 



60 



1 







14 



75 



17 



3 



31 



36 



72 



152 



22 



84 



10 



7 



18 



119 



18 



1 



15 



13 



13 



42 



23 



106 



5 



7 



17 



135 



19 



8 



12 



22 



19 



61 



24 



403 



26 



50 



73 



552 



20 



1 



6 



3 



18 



28 



25 



301 



35 



49 



74 



459 



21 







1 



1 







2 



26 



320 



25 



35 



64 



444 



22 



2 







2 



2 



6 



27 



232 



19 



28 



134 



414 



23 







3 



3 



7 



13 



28 



372 



74 



80 



255 



781 



24 















3 



3 



Mar. 1 



340 



109 



114 



218 



781 



25 















2 



2 



2 



104 



54 



92 



285 



535 



26 



1 







1 



1 



3 



3 



300 



188 



258 



553 



1,299 



27 











4 



3 



7 



4 



191 



104 



115 



304 



714 



28 















7 



7 



5 



37 



93 



109 



269 



508 



29 























6 



26 



34 



87 



215 



362 



30 



1 



1 











2 



7 



13 



50 



60 



315 



438 



31 























8 



9 



38 



14 



158 



219 



Apr. 1 















3 



3 



9 



18 



89 



77 



602 



776 



2 























10 



18 



114 



109 



256 



497 



3 











1 







1 



The first adult thrips were collected on February 15, but a very 

 few individuals had been found in blossoms previous to this time. 

 On February 18 they were numerous in one of our experiment 

 orchards, and by February 25 they were common in all orchards. 

 Maximum emergence begins about February 19 and continues until 

 about March 16, a period of three and one-half weeks. A few strag- 

 gling individuals continued to come out during all the latter part of 

 March and a very few even in April. Practically all thrips, however, 

 are out of the ground by March 20. 



The emergence period for thrips in orchards in Contra Costa and 

 Solano counties seems to be three or four days earlier and this will 

 probably hold true also for orchards along the Sacramento River. 



