16 Trans. Acad. Sci. of St. Louis. 



SAMIA CECEOPIA. 



In the paper already referred to we paid most atten- 

 tion to the Cecropia moth, chiefly because this species 

 could be procured in greatest numbers. In this paper 

 we deal with five additional lots of this material under 

 normal conditions, and three lots (controls) which will 

 be taken up in detail later. The five lots are as follows : 



River des Peres (St. Louis) normal cocoons. 

 River des Peres fluffy cocoons. 

 South St. Louis cocoons. 

 New York cocoons. 

 Fall River cocoons. 



Before going into the details of this work, it may be 

 well to give a brief resume of the previous experiments. 



The River des Peres Cecropia population emerging 

 in the spring of 1910 split up into two distinct lots; all 

 of the moths which emerged early, April 13 to May 14, 

 lived long lives (the mean for this portion of the popula- 

 tion was 16.65 days), while all of those which emerged 

 late in the season, May 14 to June 17, lived short lives 

 (the mean for this group being 10.14 days). In 1911 this 

 splitting up did not occur, but the three lots of material 

 known as the St. Louis Cecropias 1911, the New York 

 Cecropias 1911, and the Incubator Cecropias 1911, gave 

 a mean duration of life of 7.71 days, 8.06 and 8.00 days 

 respectively. This gave a clue to the following hypo- 

 thetical explanation. The 1910 material began to 

 emerge in April, a month earlier than usual. This ab- 

 normally early emergence was perhaps due to the excep- 

 tionally warm month of March, and when the unusually 

 cold weather followed in April the animals lived notice- 

 ably longer than usual. It was thought that the cold 

 was directly responsible for this long life since they were 

 numb and remained quite inactive, and hence expended 

 little or none of their reserve energy, and that those 

 moths which emerged later found the weather warm and 



