68 MASS. EXPERIMENT STATION BULLETIN 233 



old boxes, in and around packing sheds; in fact, almost anywhere where 

 fruit is gathered and stored at time of harvest. 



The overwintering larvae comprise those first brood larvae which did 

 not transform to moths the same season, and all of the second brood larvae 

 which developed in late summer or early fall. The majority of the first 

 brood larvae spin their cocoons in the orchard, while many of the second 

 brood larvae are harvested with the fruit and constitute the greater part 

 of the "worms" which spend the winter in packing sheds and storage houses. 



Spring Brood. 



Pupation. The first step in seasonal development is the pupation of 

 these overwintering larvae. This begins about the time the fruit buds of 

 the apple first show pink, usually the last of April or early in May, and may 

 continue for six to eight weeks. 



The time when a larva matures, or the brood to which it belongs, does 

 not appear to determine the time of its pupation. Second brood larvae, 

 maturing in September or October, often pupate as early in the following 

 spring as do first brood larvae which left the fruit in June. Larvae of the 

 same brood and age often pupate from two to eight weeks apart. The 

 last few stragglers to pupate, however, were always second brood larvae. 

 The time spent in the pupal stage, in the seasons covered by our studies, 

 averaged twenty-two to twenty-four days for those larvae transforming be- 

 fore the middle of May. The period gradually shortened as the season 

 advanced and warmer weather approached. In late May and early June 

 the insects spent ten to twelve days in the pupal stage before transforming 

 to moths. 



Moth Emergence. Depending somewhat on the season, moths begin to ap- 

 pear the middle to last of May, at which time, or shortly after, apples are 

 in full bloom. The period of moth emergence is shorter than that of 

 pupation since tlie time spent as pupae decreases as the season advances. 

 Most of the moths appear within five to six weeks, with a few stragglers 

 emerging in the following week or ten days. 



In Massachusetts, there has been a tendency for moths to emerge in 

 large numbers at two rather widely separated periods. The first of these 

 falls with regularity close upon the time of the "caljTc" or petal fall spray. 

 Following this is a period of rather slight emergence for two to three weeks, 

 with a sharp rise to a second peak of great emergence usually three to four 

 weeks after the first. Around this second peak is usually the greater part 

 of the total emergence, a fact which makes it desirable to know each year 

 when it occurs, so that cover sprays may be accurately timed. 



This concentration of moth emergence into two rather widely-separated 

 peaks appears to be due chiefly to weather conditions. In Massachusetts, 

 the transition from winter to spring is usually marked by warm and favor- 

 able weather which hastens all seasonal development. There usually fol- 

 lows a period of cold, inclement weather which continues sometimes well into 

 June, when development is slowed up until the approach of more uniformly 

 warm weather. The insect in all stages is very sensitive to climatic condi- 

 tions. This explains why in 1925, when a period of very high temperature 

 was encountered early in June, seasonal development was speeded up very 

 noticeably and the second peak of moth emergence occurred but two to 

 three weeks after the first. 



