52 
tooether and plant food is scarce, thej' may develop cannibalistic pro- 
pensities and begin feeding on adjacent nnhatched eggs. Owing to 
the wa}" the eggs are scattered about in nature, such an occurrence 
must be rather rare under normal conditions. 
PERCENTAGE OF EGGS THAT HATCH. 
In all lots of eggs laid by fertile females, the percentage that fail to 
hatch is so small that it was disregarded except in a few cases where 
careful counts were made. These show that of 493 eggs 6 did not 
develop, giving an average of 1.22 per cent, or about 1 in a hundred. 
This is doubtless the approximately correct percentage for the hatch- 
ing of eggs laid out of doors. 
LENGTH OF THE EGG STAGE. 
During the summer of 1904 a long series of observations was made 
in the laboratory b}" Mr. A. A. Girault to determine the length of the 
egg stage at different dates during the entire season and at varying tem- 
peratures. In all, the developmental period for over 1,300 eggs was 
recorded. These results may be tabulated as follows: 
Table XIV. — Length of the egg stage at different dates throughout the season at Paris, 
Tex., 1904. 
■ 
Date of hatching. 
Length. 
Date of hatching. 
Length. 
Date of hatching. 
Length. 
April 14 
Days. 
June 23 
- Days. 
f 
3 
if 
2i 
August 31 
Days. 
21 
2i 
April 15 
April 21 
R ! 
June 26 
September 1-^ 
91 
April 28 ' ! 5i 
June 27 
Septenil)er ''o 
3^ 
Mavis 
4i 
11 
■' 
JulvlO 
ol 
Mav '^0 
Jul V 12 
October 9 
October 12 
li 
Mav28 
Julvl3 
ii 
4 
May 29. 
Julvl.S 03 
October 14.. 
December 1 
4* 
Mav 30 
Julvl9 
2I 
9i 
17 
Julv25 
Aug. 5 3 
A clearer conception of the vaiying length during the season may 
be had from the following curve (figure 1), which is based on the data 
given in the table: 
In general it is seen that during the warmer parts of the season the 
egg period is much shorter than in the spring and fall. Although the 
embryonic period is thus inversely proportionate to the temperature, 
it is not so in any constant ratio. A number of calculations regarding 
the sum of effective temperatures^' to which different lots of eggs have 
« Following the theory of Merriam (Nat. Geog. Mag., VI, 229-238, 1894), the sum 
of mean daily temperatures above 43° to which the eggs had been exposed during 
development was calculated with the following result: Lot 1, April 14-22, 189°; 
Lot 2, June 22-25, 111°; July 15-18, 105°; November 1-17, 203°. Assuming 45° to 
mark the inception of embryonic development, the figures agree somewhat more 
closely: 173, 105, 100, 169. The summer sums are lower than the spring ones in 
either case. 
