THE CALIFORNIA PEACH BORER. 71 



characteristic habit of the larva in the open field. Whatever the 

 surrounding conditions they sought protected places first where they 

 could easily penetrate to the tender inner bark. The larva? in these 

 experiments fed freely after a period of three weeks, when many of 

 them were about one-eighth of an inch in length. 



In the open field many larva? enter the trees through old burrows, 

 thus at once finding protection in the inner bark. Newly hatched 

 larva? have been kept in vials and fed on apricot leaves for several 

 weeks, and they probably could have been kept much longer if fresh 

 leaves had been properly supplied. 



PERIOD WHEN ENTERING TREES. 



It is seen in Table V, p. 79, that a few moths begin to fly about the 

 1st of June, that they are flying in maximum numbers during July 

 and August, and that few are flying during September. Table I, 

 p. 69, shows that the egg period lasts about two weeks, as oviposition 

 begins immediately after the moths emerge. Consequently the larva? 

 begin to enter the trees during the last half of June, and they enter 

 in maximum numbers during July and August and the first half of 

 September. The last larva? would be hatching and entering the trees 

 during late September or possibly during early October. 



CHARACTER OF INJURY. 



Peach-tree borers usually live below the surface of the ground, but 

 under certain conditions and on rare occasions they are to be found 

 attacking the trunks and even the large branches. The silver prune 

 is subject to attack in this way, and frass and the exuding gum are 

 often found on the larger branches several feet above the ground. 

 When a tree becomes completely girdled the worms move upward or 

 downward into the still-living tissues, and many worms in this way 

 may encircle and eat all of the sap wood for from 12 to 16 inches 

 above the surface of the ground. This usually occurs during the 

 spring, when there is a general upward movement and when the 

 worms are preparing to pupate. 



NUMBER OF BROODS AND LENGTH OF LARVAL PERIOD, AS SHOWN BY " WORMING" 



RECORDS. 



The long period in which the larva? are entering the trees results 

 in a great variation in the size of the larva? at any time of the year. 

 This has led to the belief that there may be more than a single annual 

 brood. Numerous worming records indicate, however, that the 

 insect is strictly single brooded. It often lives less than a year, 

 but seldom longer. Larva? that hatch in the early spring or summer 

 change to moths early during the following season. Unfavorable 

 conditions will delay a few, which will mature in midsummer or fall, 

 and in this case their life period is longer than twelve months. Larva? 



