3ii7 



they are rather irregular. There is a corresponding one between 3,384 

 and 4.;04 units, and one between Gfi'ri and 8,424 units in the diflferent 

 years at Ohiey. These units, however, were not determined on the basis 

 of spring larvae, and the totals may need correction; factors other than 

 temperature and humidity no doubt enter into the time of pupation. The 

 moths from the last group of pupations should be closely watched by 

 practical men as a guide for extra sprayings in years when hibernating 

 larvae are abundant.* 



Abundance of Hibernated Larvae as Affected by Weather 

 OF Preceding Autumn and Winter. 



\\'hen the mean monthly temperature and rainfall in autumn and 

 winter are mainly within the limits shown in Fig. 5 A (p. 353), that 

 is, when the autumn and early winter are "wet and not too cold," high 

 survival and rapid development proportional to spring conditions may be 

 expected. This statement is based chiefly upon 1914, in which the moths 

 were very abundant. The fall and winter conditions of that year were 

 essentially duplicated in 1925-26, with an almost 95 per cent survival, 

 according to the observations of Mr. Flint and the Illinois field men. The 

 diagrams in Fig. 5, however, were based on the 10 years, 1913-24. Mini- 

 mum winter temperatures have not been especially considered but should 

 be carefully checked against spring survival by field men. 



The great abundance of moths in Illinois during the summer of 1926 is 

 traceable to the large numbers of hibernated larvae and the very favor- 

 able weather conditions during May and June. Not since 1914 has there 

 been such heavy damage to orchards over the state as in this year. Recent 

 experience thus proves the need of more accurate methods in order to 

 control the insect in unusual years. 



* The occurrence of darkne.ss and temperatures above 62° F. during egs-\a.ying 

 periods should also be carefully considered, as these conditions have a great deal to 

 do with the abundance of moths (Isely and Ackerman, 1923, Arkansas Agricultural 

 Experiment Station Bulletin No. 1S9). 



