70 



DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Table LXX. — Temperature records taken in the outdoor rearing shelter, showing maxi- 

 mum, minimum, and average daily temperatures, Douglas, Mich., 1911. 



Temperatures below 20° F. not recorded. 



COMPARATIVE LIFE-HISTORY STUDIES FOR THE SEASONS OF 

 1909, 1910, AND 1911. 



On considering the seasonal variations in the time of transforma- 

 tion and the relative abundance of the codling moth it is evident 

 that the climatic conditions, and mainly the temperature, are the 

 direct governing factors. Sometimes a scarcity of fruit may mate- 

 rially reduce the normal abundance of the codling moth. The effect 

 of climatic variations upon the life of the insect is particularly 

 noticeable in the spring, when the relative earliness of the season is 

 followed by a corresponding change in the time of emergence of the 

 moths. From the curves of figures 1, 6, and 14, which represent the 

 time of emergence of the spring moths for the respective years of 

 1909, 1910, and 1911, with temperature records for the last two 

 years, it will he noted that under prevailing uniform temperatures 

 the emergence for the main portion of the moths becomes limited 

 to a short period, as occurred in 1910, while on the other hand unxler 

 fluctuating temperatures the emergence is very irregular and extends 

 over a much longer period of time, as observed in 1911. 



