138 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
North Platte are on the same parallel, and Mr. Stolley's locality is about 
midway between them in the same valley or plain we may take t lie mean 
of the records of these two places, which differ very slightly, as repre- 
senting that of Hall County. 
In this case the eggs were deposited August 13 and 14, 187G, and 
began to hatch April 13 and 14, 1877. 
The number of days during which the maximum temperature was 50° 
oi over, and also the number of days during which it was 60° or over, 
were as follows: 
Months. 
50° «P 
Aueuat 17 
September 29 
October 27 
November 10 
December 3 
January 
February 12 
March 13 
April 11 
Total 
17 
28 
U 
4 
1 

1 
5 
6. 
122 
81 
In order to ascertain the number of hours they were exposed to these 
degrees of heat, respectively, we will follow Professor Abbe's estimate 
as nearly as possible, keeping in mind and making proper allowance for 
the difference between the surface temperature and that at which the 
eggs are placed. We obtain the total number of hours the eggs were 
exposed to the degree of heat specified by multiplying the number of 
hours during a day in which the maximum was at or above the given 
degree by the number of days given above each month. 
"7- 
c o 
o 
M 
o 
> 

o 
3 
— 
o 
5 
o 
> 
a 
a 
H* 
u 
t 
B 
o 
— 
s° 
u 
9 
u 
H 
B 
o 
4a » 
Months. 
umbe 
ours 
- 
2 
3 
CO 
5 
•o( 
i mm 
roduc 
houi 
_ 
ours 
>> 
« 
— 
so 
c! 
S . 
~ o 
o a 
5| 
a — 
c 
- 
to 
as 
to 
-z 
as 
August 
24 
17 
408 
22 
17 
374 
September 
22 
29 
638 
18 
28 
504 
18 
27 
486 
12 
19 
228 
November 
11 
10 
110 
6 
4 
24 
December 
4 
3 
12 
4 
1 
4 






8 
12 
96 
4 
1 
4 
10 
13 
130 
6 
5 
30 
12 
11 
132 
10 
6 
60 
Total 
122 
2, 012 
81 
1,228 
Prom this we see that if 50° be taken as the minimum, it requires 
2,012 hours, 1,228 of which must be above 60°, to hatch the eggs in the 
latitude of Grand Island, Hall County, Nebraska; or, to be more exact, 
784 hours between 50° and 60°+ 988 hours between 60° and 75° + 240 
hours above 75° =2,012 hours. 
Let us take another case ; and this time we will select one at North 
Platte, Nebr., one of the points selected by Professor Abbe in illustrat- 
ing his theory. With the explanation given above, the following table 
will be understood. Eggs were deposited from July 10 to 25, in 1870. 
