421 



Pig. 28. Showing rainfall and mean temperature and humidity for the 

 summer of 1915, 1916, and 1917 at Olney, Illinois. (See Table XI.) The pupa, 

 egg, apple, and cocoon curves are plotted with reference to a standard or aver- 

 age time as follows: — The standard or average is plotted as 100; pupal scale, 

 upper left; egg scale, middle right; apple and cocoon scale, lower left. The 

 data are plotted on the median date of the first and last occurrence in each 

 group of 30 pupae, 50 eggs, and 10 larvae in the apple and in the cocoon, a 

 dot marking the first and the last dates of each series. Correlations of time 

 (length of stages) with rainfall and rising and falling temperatures are indi- 

 cated. 



