45 



tures to which the insects were .subjected. Many other records are 

 questionable by reason of the fact that the generation, or the nearness 

 to the maximum of the generation, of the insects phiced in the cage 

 was uncertain or unknown. 



Early in his studies of the life histor3' of this insect the writer saw 

 the necessity of finding some method by which the numbers of indi- 

 viduals, of a generation could be approximated at certain times. By 

 an incidental study of the records of larvfe captured under bands, 

 published by Professor Aldrich in 1900, it was noted that at a certain 

 time in the season there were fewer larvje so caught than at periods 

 of time immediatel}^ following and preceding. By collecting as many 

 records as were obtainable at that time, it was observed that these 

 conditions were quite constant. Tlie periods of the larger and smaller 

 number were termed, respectively, the maximum and mininuim of 

 larvae entering bands. 



In 1901 many fruit growers in Idaho, at the request of the writer, 

 kept and submitted records of the larvte killed under l)ands. Other 

 records, many of which had been made without any idea of the future 

 use to which they might be put, were collected from many sources. 

 These records were tabulated and curves were drawn upon cross-sec- 

 tion paper, using the time as one factor and the number of larvse as the 

 other. These curves give quite an accurate picture of the course of the 

 insect in the orchards throughout the season. Not all of the records, 

 however, were satisfactory, as a few of them from various causes gave 

 data which were of no value. The curve showing the efl'ective tem- 

 perature at the dates at which the larvae were killed under the bands 

 was drawn upon the same charts and gives quite accurately the effect 

 of the temperature upon this habit of the insect. A number of these 

 records are reproduced (figs. 5 to 16). 



INACCURACIKS OF THE RECORDS. 



There are many sources of possible inaccurac}^ in these records. 

 The greatest inaccuracy is probably found in the weekly or biweekly 

 band records, because these are composite records of many individual 

 trees and show only approximately the dates of the maxima and min- 

 ima. Man}^ of the records were commenced too late in the season to 

 be of an}" real value; and when they were started even a little late the 

 curve ascends with rapidity, which would not have happened had the 

 record been started earlier. In consequence of a series of warm da3'S, 

 the maximum number of larvre may enter the bands sooner than they 

 would if the temperature had remained normal; and if the temperature 

 be low for many daj^s, the maximum might be later than it would be 

 normarll3^ Spraying might seriously interfere with the accuracy of 

 the record, as at certain periods all of the larva3 entering the fruits 

 might be killed and thus cause a fall in the curve of larva? entering 



