EFFECTS OF VAKIATION IN TEMPERATURE ON THE EGGS. 127 
Precisely the same rule holds good here as in the preceding table. The 
•chief variations are in the months of December, January, February and 
March. 
If the excessive increase of locusts depends to any considerable degree 
upon the temperature, and this excessive increase is the exception and 
not the rule, then we must seek for the cause in the abnormal conditions 
of the temperature. These we see from the foregoing table are found 
chiefly in the winter of the year, the variation in the means of the sum- 
mer months being comparatively unimportant. 
The condition as to moisture must, as a matter of course, be combined 
with that of temperature in making the direct application and compar 
ing the locust years with the non-locust years, but at present we are 
only endeavoring to ascertain if possible in what respects the records of 
temperature show a variation likely to affect the increase or development 
of the locusts. 
As the eggs are deposited before December, and do not hatch out in the 
northern latitudes of their native habitats until after March, it follows 
that if the excessive changes of this part of the year affect them in any 
way it must be by their action upon the eggs. But the facts presented in 
our first report tend to the conclusion that the eggs of C. spretus are 
but little affected by changes of temperature. 
There are some other facts presented in Table VI worthy of notice. 
If we compare the winters preceding the locust years with those of 
other years, we find that in the series 1873 to 1877, as a rule, the former 
were warmer than the latter. 
Variations between months of consecutive years. 
Tears and stations. 
December. January. February. 
Mean. 
BRECKENRWGE. 
J873-74 
1874- 75 
1875- 76 
1876- 77 
1877- 78 
FORT SULLY. 
1873- 74 
1874- 75 
1875- 76 • 
1876- 77 
YANKTON. 
1873- 74 
1874- 75 " ' 
1875- 76 
1876- 77 
FORT BENTON. 
1872- 73 
1873- 74 
1874- 75 
1875- 76 
PEJIBINi. 
1873-74 
1875- 76 
1876- 77 
1877- 78 
8.0 
12.8 
18.1 
0.1 
23.3 
14.9 
26.9 
27.0 
13.7 
18.1 
23.0 
27.3 
12.2 
11.3 
13.7 
29.6 
36.8 
6.6 
8.1 
-6.3 
-27.4 
2.3 
-9.5 
6.3 
-0.9 
14.7 
16.1 
0.1 
18.7 
13.9 
15.6 
0.6 
18.9 
13.6 
16.5 
11.3 
-8.6 
13.9 
-3.0 
-2.6 
-5.2 
11.2 
8.0 
-7.9 
4.3 
21.5 
27.4 
20.3 
4.2 
14.4 
33.4 
18.8 
2.5 
20.7 
36.4 
18.4 
22.4 
13.9 
16.7 
2.6 
-4.5 
17.4 
25.5 
6.1 
- 1.5 
9.6 
6.9 
23.5 
17.1 
10.4 
20.0 
20.3 
17.5 
8.7 
22.3 
20.7 
15.4 
15.8 
1L6 
22.5 
2.1 
0.3 
2.0 
21.4 
