424 



If nunibei- of spinnings has any effect, the evidence indicates that it 

 decreases the length of stages. In an experiment in 1920 there was no 

 difference in the length of pupal life related to number of spinnings. A 

 decrease in time might be inferred from Bishop's ('2:5) work on the 

 honeybee larva. In the codling moth, it may be assumed that the in- 

 creased acidity due to several spinnings helped to complete processes 

 which are essential to rapid development, and which take place over a 

 long period. 

 (7.) Seasonal March of Temperature and Humidity. 



Fig. 2!) shows the average daily variation of temperature and 

 humidity for the different generations at OIney. The curves are roughly 

 drawn through the plotted records of temperature and humidity as shown 

 in Fig. 17, and they represent the conditions encountered by several sets 

 of pupae. Although slightly different from the curves which would result 

 from the use of data unselected from a biological point of view, they serve 

 to indicate the marked difference between different seasons and thus 

 emphasize the reason for taking humidity into account. 



..0/234?g7a3 0/23 



Fig. 30. Ball-Taylor diagrams and hythergraph of scarce and abundant 

 codling-moth years in Southern Illinois localities. 



