290 
Psyche 
[December 
represent Cape Cod. The information contained in these tables 
has been computed from records of the United States Weather 
Bureau and information is restricted to localities for which this 
Bureau obtained detailed records during the periods covered by 
this study. The records were mostly of maximum and minimum 
daily temperatures^ columns headed “total amount of tem- 
perature below 32 degrees’^ and “total amount of temperature 
below 0 degrees” being obtained by adding minimum temperatures 
experienced at each locality. The information contained in these 
tables is presented as comparisons between different localities 
and as a comparison of the two winters. They are not intended 
to show that any one set of factors explains the variation in 
winter mortality that was found in the several localities where 
experiments were placed. 
Several interesting points may be noticed in a study of these 
tables; 1, the moderating effect of the sea is shown in those 
stations that are located on the sea coast i. e., Portland, Me., 
Rockport, Boston, Plymouth and Provincetown, Mass. 2. 
In all localities the fact that the winter of 1922-1923 was severe 
in comparison to the mild winter of 1923-1924, is clearly in- 
dicated. The mortality rate for each winter is for the most part 
readily compared with this difference in severity. 3. A distinct 
correlation is shown for the winter of 1922-1923 between high 
percentages of mortality and winter severity. 
It does not appear that a slow westward spread of this insect 
in New England is to be accounted for by winter mortality ex- 
cept that barriers of high mortality may in severe winters appear, 
such as was represented by Concord, Mass, during the severe 
winter of 1922-1923 when mortality there was found to be 30 
per cent. Worcester, Mass., the station located farthest west in 
the experiments of 1922-1923 showed 2.8 per cent of mortality 
(table 4) and in the experiments of 1923-1924 the average winter 
mortality of the six stations located farthest west in Massa- 
chusetts was but 3.6 per cent. 
To the north, however, it does seem that the insect may be 
entering territory in which it will suffer annual winter mortality 
sufficient to keep its numbers below that which would allow 
serious injury to crops, at least in certain areas. In Merriam^s 
