THE CODLING 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 larvae 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 u 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 larvae 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 larvae and the taking of the 

 measurements. 



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

 ments in millimeters for each instar, Douglas, Mich., 1-910. 



No. of ob- 

 servation. 



First instar. 



Second instar. 



Third instar. Fourth instar. 



Fifth instar. 



Hatch- 

 ing. 



Mn„ 



First 

 molt, 



Mm. 



Second 

 molt, 



Mm. 



Third 

 molt. 



Mm. 



Fourth 

 molt. 



Mm. 



1 



Aug. 11 



Aug. 12 

 ...do 



Aug. 10 

 ...do..... 



...do 



...do 



...do 



Aug. 20 



0.33 

 .33 

 .33 

 .33 

 .33 

 .33 

 .33 

 .33 

 .33 



Aug. 15 

 Aug. 16 



...do 



Aug. 21 



...do..... 



...do 



...do 



...do 



Sept. 3 

 Sept. 1 



0.50 

 .45 

 .50 

 .48 

 .55 

 .55 

 .46 

 .50 

 .40 

 .48 



Aug. 22 

 Aug. 20 

 Aug. 23 

 Aug. 27 

 Aug. 25 



...do 



(») 

 Sept. 1 

 Sept. 7 

 Sept. 5 



0. 66 

 .66 

 .63 

 .66 

 .73 

 .70 



Aug. 27 



...do 



Sept, 5 



( 3 ) 

 ( 3 ) 

 ( 3 ) 



1.00 

 1.03 

 1.00 



.91 



Sept. 8 



( 3 ) 

 Sept. 1 

 Sept, 12 



1 40 



2 





3 



4 



1.30 

 1.20 



5 





6 

















8 



.70 

 .65 

 .65 



( 3 ) 

 Sept. 22 

 Sept, 12 









9 



.87 

 .83 



( 3 ) 

 Sept. 21 





10 



...do 32 



1.06 



No. of ob- 

 servation. 



Sixth instar. 



Pupation. 



' Days duration of instars. 



Fifth 

 molt. 



Mm. 



Sixth 

 molt, 



First 

 instar. 



Second 

 instar. 



Third 

 instar. 



Fourth 

 instar. 



Fifth 

 instar. 



Sixth 



instar. 



1 



Sept. 20 



1.60 



o 

 5 ft 



c3 

 ft 



4 



4 

 4 

 5 

 5 

 5 

 5 

 5 

 14 

 12 



7 

 4 

 7 

 6 

 4 

 4 



5 

 7 

 4 

 9 



12 



12 





2.... 





3 



Sept, 18 

 Sept. 22 



1.53 

 1.50 



5 



7 



17 



10 





4 



B 



5 

















S 















.s 



8 







11 

 4 

 4 









fe 



9 







15 



7 









10 



( 4 ) 





9 



m 





































i Bui. 80, Part I, Bur. Ent. 



2 Psvche, vol. 5, p. 420. 



3 Died. 



4 Wintered. 



U. S. Dept. Agr., 1909. 



