353 



Fig. 4. Ball-Taylor diagrams of temperature and rainfall. A is for a typi- 

 cal year when codling moths are abundant in Southern Illinois; B is for a 

 typical year when they are scarce. The numbers 1 — 12 on each diagram in- 

 dicate the months January — December, and the cross beside each number in- 

 dicates the amount of rainfall and mean temperature for the month. (5i = 1st 

 half of May. 5= = 2d half of May.) Note that in the abundant year the rain- 

 fall is comparatively heavy (4 — 5 inches) in September, October and November 

 and comparatively light (1 — 3 inches) in the spring and summer; while in the 

 scarce year it is light (1 — 2 inches) in the autumn and winter and heavy (4—6 

 inches) in the spring and summer. Note also the higher temperatures in May 

 (Sa), June (6), and July (7) in the abundant year. 



