THE CODLINc; MOTH IN MICHIGAN. 



77 



stages and its habit of feeding within the fruit, where it can not 

 readily be located for observation without great care and labor. 

 Mr. E. L. Jenne, 1 in his studies of the codling moth in the Ozarks, 

 determined the number of molts of the larva3 by rearing them on 

 small pieces of fruit in glass vials. The vials were frequently exam- 

 ined for the cast skin of the head, and on this basis the number oi 

 molts was established. Jenne encountered great difficulty in 

 preventing the fruit from rotting and in maintaining the larvae in a 

 healthy condition. His records from 12 larvae showed that 9 larvae 

 passed through 7 instars and 3 larvae passed through 8 instars. 



At Douglas, Mich., the writer, in determining the larval molts, 

 made use of Dyar's 2 method of head measurements, on the basis 

 that ''the widths of the head of the larva in its successive stages 

 follow a regular geometrical progression." By this method the 

 necessity of finding the cast skin was eliminated and the larva; could 

 be reared in entire fruit or in large pieces of fruit. On the other hand, 

 this practice involved a considerable amount of labor and additional 

 difficulties both in the finding of the larva 1 and the taking of the 

 measurements. 



Table LXXIV. — Instars of the codling moth larvae of the second brood, and head measure- 

 ments in millimeters for each instar, Douglas, Mich., 1910. 



No. of ob- 

 bot ration. 



First instar. 



Hatch- 

 ing. 



Aug. 11 



Ail?. 12 



.do. 



Aug. 1(> 



..do 



..do 



..<lo 



..do 



Ant;. 20 

 ..do 



Mn, 



o. 33 

 .33 

 . :;:; 

 . 33 

 .33 

 .33 

 .33 

 .33 

 .33 

 .32 



Second instar. 



First 

 molt. 



.Nil-. 

 Aug. 

 ..do. 

 Auk. 

 ..do. 

 ..do. 

 ..do. 

 ..do. 

 Sept. 

 Sept. 



Mm. 



0.50 

 .45 



. 50 

 .48 



. .').') 



. 55 

 . 46 



.511 

 .40 

 .48 



Third instar. 



Second 



molt. 



Auk. 

 Auk. 

 Auk- 

 Auk. 

 Auk. 

 ..do. 



m 



Sept. 

 Sept. 



Sept. 



Mm. 



Fourth instar. 



Third 



molt. 



0.66 



. 66 

 .63 

 .66 

 .73 



.70 



Auk. 27 



..do 



Sept. 5 



< : > 

 ( 3 ) 



( 3 ) 



Sept. '_>L> 



Sept. 12 



Mm. 



1.00 

 1.03 



1.00 



.9] 



.87 



.Si! 



Filth instar. 



Fourth 

 molt. 



Sept. 8 



Sept. 1 

 Sept. 1-' 



„ (3) 

 Sept. 21 



Mm. 



1.40 



1.30 



1.2(1 



No. of ob- 

 servation. 



Sixth instar. 



Fifth 

 molt. 



Mm. 



Pupation. 



Sixth 

 molt. 



Se 



Days duration of instars. 



First 



instar. 



Second 



instar. 



Third 

 instar. 



Fourth 



instar. 



Fifth 

 instar. 



(') 



Sixth 

 instar. 



1 Bul. so. Part 1. Bur. Km., ('. S. Dept. Agr., L909. 

 - Psyche, vol. 5. p. 420. 

 ■ Died. 

 ' Wintered 



