' 



27 



The final molt requires about thirty minutes. The skin splits open 

 over the front of the head and slips down along the proboscis and 

 back over the prothorax. The skin clings to the antenna? and the tip 

 of the proboscis till after the dorsum has been uncovered and the legs 

 kicked free. Then by violently pulling upon the skin with the fore 

 legs first the tip of the snout and then the antenna? are freed, and 

 finally the shrunken and crumpled old skin is kicked off the tip of 

 the abdomen by the hind legs. 



LENGTH OF PUPAL STAGE. 



The length of this stage is more easily determined than that of any 

 other. It seemed to make little difference in the time whether the 

 pupa? were allowed to remain in the squares or removed therefrom. 

 Considerable variation in the length of this stage exists among indi- 

 viduals of the same generation and even between offspring of the 

 same female and from eggs laid on the same day. The period of 

 investigation ranged from Jury to December, so that the extremes of 

 the season are included. Altogether over 450 observations were made 

 upon the length of this stage. Nearly all of these are included in 

 Table I\ r , which shows a summary of the results. 



Table IV. — Tabular arrangement of observations upon the length of pupal stage 



in squares. 



Period of examination. 



Number feS* 



of obser- 



length 



vations: <*JES- 



Average Ave rage Total 



lelo-th ; eff ective ! effective 



of stacre tempera- tempera- 

 or STa a e. tm , e _ tm , e _ 



1902. 

 July6to31 



September 15 to October 3 . 

 September 24 to October 28 



November 2 to 13 



December 2 to 29 



Uil 

 81 

 L67 



2 to 5 



3 to 7 



4 to 8 



5 to 6 

 10 to 16 



Days. 

 3.5 

 5.2 

 6.0 

 5.6 

 14.5 



°F. 

 39. 65 

 36.05 

 31.1 

 26.2 

 18.55 



F. 



138.8 



187.5 



186.1 



146.7 



269.0 



It should be noted in connection with Table IV that the observa- 

 tions made in November were during a period of rather warm weather 

 and that the temperature records for that time are incomplete. It is 

 likely that the average effective temperature given for that period 

 might be different were the records comx3lete. 



The average length of this period during hot weather is from three 

 to four days, and the period increases as the cool fall weather 

 approaches to a maximum of about fifteen days. 



A comparison of Tables I, III, and IV shows that the decrease in 

 temperature affects each stage in very nearly the same proportion. 

 In each case the maximum recorded length of any stage is about four 

 times its minimum, and the great retardation in each case occurs 

 somewhere between 60° and 70° F. of mean average temperature, or 

 17° to 27° F. of effective temperature. Even greater retardation 

 occurs during the winter season. 



