407 



Six sets of about 20 larvae each, which were kept in conditions supposedly 

 suitable for late summer pupation, all died, (a.) Three sets collected August 

 23d. August 26th. and September 19th. totaling 58 larvae, were held at a tem- 

 perature of 87° F. and humidities of 80. 60, and 40 per cent, respectively. All 

 larvae in the two sets at the lower humidities died by October 9th, while those 

 in the moistest condition lived to January. There were no pupations, (b) 

 A single set collected August 23d and kept at 90' F. and 55 per cent humidity 

 all died by October 9th. (c) A set collected July 26th and kept at 46°— .57° F. 

 all died without pupation by November 14th. (d) A set collected September 

 10th and subjected to daily variations of temperature between 80° and 100° F. 

 and a mean humidity above 90 per cent, all died by December 19th without 

 pupation. 



Five other sets of autumn larvae, which had been kept under conditions 

 the same as the above six sets, were transferred on or before December 19th 

 to an approximately constant temperature of 70° — 75° F. and a 90 per cent 

 humidity, (a) Larvae collected September 10th and held at a temperature 

 with daily variation between SO and 100° F., and a variable humidity with 

 mean about 60 per cent, were transferred to 75° F. on November 20th; and 

 all died by March 20th without pupation, (b) Others kept at 65° F. and 40 

 per cent humidity and transferred to 75° F. on November 25th, all died by 

 December 19th, without pupation, (c) A set collected September 19th. kept 

 at a temperature varying from 40° to 76° F. to February 15th, and then trans- 

 ferred to a constant temperature of 70° F., showed one pupa, (d) A set col- 

 lected August 28th was kept at 77° F. and a humidity of 95 per cent until 

 October 2oth, and then transferred to 70° F. By March 19th, five had pupated, 

 and the others had died, (e) A set kept at 62° F. and a humidity above 90 per 

 cent was transferred to 70° F. December 19th. By February 15th, five moths 

 had emerged, and the others had died. (Note: Larvae kept at 77° F. would 

 not ordinarily pupate with the treatment described, but those in sets having 

 been subjected to a low temperature might be expected to do so under ordi- 

 nary conditions.) 



Seventy-one larvae, collected between July 25th and August 18th and fail- 

 ing to pupate under the experimental conditions designed tor pupation, were 

 kept 18-20 days below 60° F., being at 22° F. for 6 or 7 days, but failed to pu- 

 pate when returned to the experimental conditions for pupation. 



Four-hundred larvae, placed under conditions shown in Table XXII be- 

 tween August 24th and September 22d. 1917, and kept there until November 

 14th, were then submerged 20 hours in water and placed at 75° F. Those kept 

 at temperatures below 65° F. and those kept at higher temperatures subjected 

 to greatest amount of evaporation, pupated and emerged in greatest numbers. 

 Representative data are shown in Table XXII. 



For the spring experiments of 1918. 1919, and 1920, some of the hibernating 

 larvae were kept at temperatures at or below 32° F. (freezing) tor a day or 

 more, but without effect on the number pupating when placed under favorable 

 conditions. In general, no attempt to freeze the larvae was made. They were 

 merely kept at temperatures near 50° F. (This temperature proved to be too 

 high, and pupation results will be discussed later.) The stock usually reached 

 a condition where pupation would take place between December 20th and 

 January 20th, January 1st being an average date. 



In the spring experiments, larvae given uniform treatment during 

 the winter showed variation in the length of time to pupation at constant 

 temperatures, regardless of the date of leaving the apple, the date of 

 collection, and the conditions under which they were kept, either before 

 or during the period of low temperatures. In 1920 a large series of larvae 



