396 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



ON THE PUPAL INSTAR OF THE FRUIT-TREE LEAF-ROLLER 

 (ARCHIPS ARGYROSPILA WALKER) i 



By W. M. Davidson, U. S. Bureau of Entomology, Walnut Creek, Cat. 



During the summer of 1911 the writer found occasion to study the 

 pupal instar of the Fruit-tree Leaf-roller at San Jose, Cal. 



In California the larvae of this insect hatch from the winter eggs at 

 about the time when the fruit buds are just beginning to open. This 

 period varies with the season and is usually from the last week in 

 February to the third week in March, as at least three weeks elapse 

 from the time of the opening of the buds of the earliest until that of 

 the latest varieties of fruits attacked. Pears, plums, prunes, cherries 

 and apples are infested, the greatest damage occurring on the three first- 

 mentioned varieties. The larvae at first feed inside the bud and protect 

 themselves further with a web, but later they repair to the foliage and, 

 inhabiting the upper surface of the leaves, cause the characteristic 

 rolling. Pupation takes place in the rolled leaf, the chrysalis at first 

 being green and soon changing to dark brown. 



A large number of larvae, mostly in the final larval instar, were col- 

 lected May 8 and 9 and placed in a jar. Each day this jar was in- 

 spected and the pupae that had transformed were removed to separate 

 glass vials, over the mouths of which cheese-cloth was stretched in 

 order to allow of free passage of air. Out of 102 pupae obtained, 25 

 perished before reaching the adult stage. No parasites issued from 

 these twenty-five. In the field, especially towards the end of the 

 pupal period, a fair percentage of the pupae were parasitized. Of 

 the 77 adult moths which issued, 47 were females and 29 males, the re- 

 maining individual escaping before its sex could be ascertained. The 

 total average pupal period was 19.9 days, the length of the stage vary- 

 ing from 16 to 23 days. The average pupal period for the 47 females 

 was 19.8 days and for the 29 males 20.3 days. In Colorado in 1912 

 GilP found that the pupal stage occupied on the average 1 1.25 days and 

 covered a period from May 28, until the last week in June. He re- 

 cords ^ that the maximum period of pupation was reached from about 

 June 12 to June 20, and that pupae could be found in the field as late as 

 July 10. In California the writer found that the maximum pupation 

 period took place in the field about May 20, and that live pupae could 

 be found as early as April 24, and as late as July 1. 



> Published with the permission of the Chief of the Bureau of Entomology. 

 'Gill, "The Fruit-tree Leaf -roller" ; U. S. Dept. Agr. Bur. Ent. Bull. 116, pt. 5, 

 p. 98. 



s Ibid. p. 99. 



