4 BULLETIN" 252, IT. S. DEPARTMENT OF AGRICULTURE. 



successive stages of the codling inoth through the series of five cages 

 the life cycle is readily ascertained. 



It should be explained here that each table is a unit in itself. 

 Successive tables are not necessarily continuations of the life history 

 of all of the same individuals. For example, it will be noted that 

 Table I is a record of the time of pupation of 753 wintering larvae and 

 that Table II includes observations on the length of the pupal stage 

 of but 483 of these individuals. Differences of this character may be 

 due to natural or artificial causes, such as to death, to accidental 

 injury, to parasites, to the removal of specimens for other purposes, 

 and to accidental escape of the moths during examination. 



WINTERING LARV^:. 



The wintering larvae, as stated in the definition of terms, comprise 

 first and second brood larva?. These larvae winter naturally in cocoons 

 (PI. I, fig. 1), usually beneath the loose bark of trees, in decayed wood, 

 or in other similarly protected places on or about the tree. The larvse 

 are inactive until spring, when they remodel their cocoons, so as to 

 furnish exit tubes for the moths. (See PL I, fig. 2.) The exit tube, 

 which varies in length according to the exigency, assists the moth 

 in successfully emerging from the cocoon. 



The codling-moth larvae used at the laboratory were collected early 

 in the spring of 1913. These larvse were secured from cider mills 

 where they had spun up beneath the flooring and in other concealed 

 places. The larvae were then allowed to form new cocoons in racks 

 such as are shown in the illustration (PI. II, fig. 2). 



These racks consist of two strips of soft wood, to the lower of which 

 three narrow crosspieces are glued — one at each end and one in the 

 middle. A thin piece of mica is then placed between these cross- 

 pieces and the top strip and the whole is held together by two clamps. 

 This makes it possible to remove the top strip and to observe the 

 specimens through the mica. Referring to the illustration, it will be 

 seen that there are artificial cells or compartments. The walls of 

 these were first outlined with a little glue over which sawdust was 

 sprinkled. Although more than one larva frequently spins up within 

 the same chamber the artificial barriers serve to keep the larvae some- 

 what separated. Such separation facilitates the recording of the 

 observations. 



SPRING BROOD OF PUP^E. 



Time of pupation. — Daily observations of the wintering larvae were 

 taken and as each larva pupated its number was recorded upon the 

 rack directly below the pupa. (PI. II, fig. 2.) In Table I is shown 



