October, '21] i^uayle: codling moth in walnuts 441 



in trays and other places into which the larvae can squeeze for protection. 

 They are inactive in these cocoons until early spring, when they re- 

 model their cocoons so as to furnish exit tubes for the moths. 



Spring Brood of Pupae. On April 6th counts and estimates made 

 in the field indicated that in the walnut, about 10% of the wintering 

 larvae had pupated, while about 15% of those in the apple had pupated. 

 On April 19th about 20% had pupated from walnut, and 30% from apple. 

 The last pupation of this brood occurred on June 19 from walnut, and 

 about 10 days earlier from apple. The length of this stage varies from 

 18 to 30 days. 



Spring Brood of Moths. The first m.oths were seen in the field on 

 April 24. The maximum, emergence was about June 1st, and the last 

 emergence record from the apple was June 20th, and from the walnut, 

 June 30th. 



The First Generation 



First Brood of Eggs. The first eggs observed in the field were on 

 May 8th on pears. May 12th on apples, and May 14th on walnuts. The 

 maximtuTL nimiber of eggs was present on apple about June 1st, and on 

 walnuts about June 10th. It has been noted this year, as in other years, 

 that eggs occur earlier on apple than on walnut, and that eggs of this 

 brood continue to be deposited until early in July. The time of incuba- 

 tion ranges from 10 to 20 days. 



First Brood of Larvae. The first eggs obser\'ed to hatch was on 

 May 17th on apple. The peak of appearance of the larvae on walnut was 

 during the 2nd week of June. A large majority of the first-brood larvae 

 enter, or attempt to enter at the calyx end of the nut. Before all of this 

 brood enter, however, the nut becomes too hard (3rd week of June) at 

 the calyx end and entrance is sought at other points, particularly 

 where two nuts are in contact. The time spent in the nuts will av- 

 erage about 35 days. Some of this brood of larvae were still in the nuts 

 69 days after entrance, and even then showed no signs of spinning un- 

 til they were disturbed by cracking the nuts. Such records were noted 

 on August 18th and an occasional larva of this brood pass the winter be 

 fore transforming. Definite records to this effect have been noted at 

 Carpinteria and Santa Ana. 



First Brood of Pupae. The first pupation of larvae that had 

 hatched in the spring was observed on June 15th. The majority of this 



