72 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



which hatch during the midsummer or in the fall usually mature 

 during the same period of the following year. If, however, a tree 

 has been weakened or is near to its death, the borers will invariably 

 mature in the early spring or summer, when their life cycle will be 

 much less than the regular twelve months. 



Monthly worming records were made during a period of about 

 two years, and although for many reasons these records can not be 

 compared they offer much of interest. The first plan — to mark off 

 a badly infested orchard into uniform plats and to dig all of the 

 worms regularly from month to month on each of these plats — was 

 not entirely satisfactory. The infestation in any orchard is extremely 

 variable. One tree may harbor from 50 to 70 or more larvae, while 

 those immediately surrounding may be entirely immune. It was 

 necessary, therefore, to find infested trees regardless of the position 

 in the orchard when each record was made, and all worms which were 

 collected on any one date, although they may have been gathered 

 from many trees in various parts of the orchard, constituted the 

 basis for the record for that particular period. Some trees would 

 harbor 1 or 2 and others from 50 to 70 worms. (See PI. X, fig. 1.) 

 The 1907-8 records were taken mostly from large apricot trees, and 

 those for 1908-9 from apricot, prune, and peach trees. 



Table III. — Records of larvse of the California peach borer taken from trees, 1908-9. 









Num- 



Num- 













Number 





ber of 



ber of 



Total 





Number 





Date. 



of trees 



Kind of 



larvse 



larvse 



number 



Number 



empty 



Remarks. 



exam- 



tree. 



small 



half to 



of 



of pupse. 



pupal 





ined. 





to half 

 grown. 



full 

 grown. 



larvse. 





cases. 





1908. 



















May 5 





Prune 







Several 











Prunes on Myrobalan 











plum root, and not 



















badly infested. 



15 













Several 



2 



10 





 

 8 





18 













23 



19 







Many 



Many 



Pupse and empty pupal 

















cases from dead trees; 



















hence very advanced 



















stage of insect. 



24 



4 



Apricot . . . 



7 



127 



134 



19 







All trees completely 

 girdled; most worms 

 were nearly grown. 



26 



2 



...do 











15 



4 



Both trees completely 



June 18 



10 



Peach 



8 



33 



41 











girdled. 



19 



12 



...do 



11 



75 



86 



2 









20 



3 



...do 



9 



63 



72 



14 









July 14 



2 



Apricot*. . . 



2 



1 



3 



23 



17 



Trees almost com- 

 pletely girdled. 



20 



2 



...do 







12 



12 



10 



47 



Both trees completely 

 girdled. 



Nov. 5 



3 



...do 



9 



16 



25 













6 



6 



...do 



16 



46 



62 











One tree contained 8 

 larvae, 7 of which 

 were in crotches 

 above the ground. 



Dec. 8 



4 



5 

 5 



...do 







113 



67 

 89 





 



1 









 





1909. 

 Jau. 5 



..do 







Larvse were of all sizes. 



Feb. 5 



...do 



76 



13 



Larvse in this record 



















mostly small; one 



















larva in newly 



















formed cocoon. 



