THE TEEEAPIlSr SCALE. 55 



The Pupa. 



The pupal instar is one of development. In it the rudimental 

 structures of the preceding instar reach their full development. The 

 leg sheaths are mere tubes at the beginnmg of the instar; at the end 

 they contain the matured legs. The wing sheaths have a similar 

 history, being at first transparent bags, which develop gradually 

 until the last third of the instar, when the wmgs fold and the charac- 

 teristic fleshy color appears. The pupa (PI. II, d) has a pale flesh 

 color with chitinized areas upon the head and anal region. There is 

 also a crescent-shaped spot and a transverse band of a bright flesh 

 color. The antennae and legs are at first ventral, but they elongate 

 and finally appear prominently in the dorsal view. 



TIME IN PUPA. 



The pupal instar varies in length, occupying from 4 to 11 days, 

 and averages about 6 days in favorable weather. Those individuals 

 that spend only 4 days in this instar have invariably been delayed 

 as prepupse. It is very exceptional for a male to pass 8 days in the 

 pupa, even when weather conditions are unfavorable. When condi- 

 tions are such that the pupae require over 9 days, there is a heavy 

 mortality. Many die, and those that enter the adult stage mostly 

 die without leaving the protection of the puparium. 



In both 1912 and 1913 rearings were made to determine the length 

 of the pupal period under varying conditions. Observations made 

 upon the specimens in the orchard showed that most of the specimens 

 remained in the pupa 6 days. A brood that emerged July 22, 1912 — 

 that is, approximately a month after the height of the normal emer- 

 gence — ^was retarded 6 days by unfavorable conditions. Thirteen 

 males passed successfully through the pupal stage and gave an aver- 

 age of 8.15 days in the pupal instar. 



The average mean temperature for July, August, and September- 

 1912, was 71.5° F. 



A brood that emerged June 24, 1913 — that is, appproximately at 

 the height of emergence— passed through the larval instars in a nor- 

 mal manner, and the imagos left the pup aria upon the forty-sixth 

 day. These specimens were slightly retarded, owing to their removal 

 while in prepupa from the orchard to the laboratory. Fourteen of 

 these specimens passed through the pupal instar in a normal manner. 

 They gave an average of 6.2 days for the pupal instar. The fraction 

 of a day in excess of 6 days is small and is clearly due to the unfavor- 

 able environment of the laboratory. Table XXXIV gives the indi- 

 vidual record of these 14 males. The average mean temperature for 

 June, July, and August, 1913, was 73.4° F. 



