319 



ol variations in rate of development from hour to hour during the 

 warmer and cooler parts of the day, or for variations in humidity and 

 other factors ; neither did it allow for variations in developmental totals 

 in different seasons of the year. The developmental total as here 

 used permits the refinement necessary for more accurate prediction. 



For convenience in applying the results of this work to pref'i tion 

 of appearance of moths in Illinois, a table of rates of development 

 (Table I) has been prepared, and directions for its use have been out- 

 lined. This method, which is less complicated than Glenn's "day-degree" 

 method, can be used by the orchardist without an understanding of all 

 the technical terms employed in the description of the experimental work 

 or the mathematical processes by which the developmental units were 

 derived. Knowing the temperatures and other items of weather condi- 

 tions for the season, he can read the corresponding values from Table I, 

 select the proper totals from the following tables, and calculate the time 

 for the appearance of the larvae by simple arithmetic. Even in the hands 

 of a novice, who follows the rules of procedure literally, this method 

 should give more accurate results than were possible by the "degree-day" 

 method. 



Note : In order to apply the values given herein to the development 

 of the insect under climatic conditions differing from those in Illinois 

 the developmental totals will doubtless have to be modified on the bass 

 of experience (see methods of modification explained in PART TWO). 

 Further experience in Illinois may make some modificaticns desi ab.e 

 here also. 



Procedure for Predicting the Time of Emergence of Moths. 



Spring Pupae. 



a. Observe the date of the first pupation of larvae kept out of doors 

 under conditions similar to those in the orchard. 



b. On that date, or before, place a Friez hygrothei'mograph in a 

 standard weather shelter under orchard conditions, taking care to have 

 the pens read the same time for both factors recorded.* 



c. From the U. S. Weather Bureau records for the nearest station, 

 determine the total rainfall for the preceding months, Sept., Oct., Nov., 

 Dec, and Ian. From the total of these months, select from Table III 

 (p. 321) the correct developmental total for the pupal stage. 



♦ A Uiermograph and a sling psychrometer may serve instead of the hygrother- 

 mograph. 



