36 
PLANT-BUGS INJURIOUS TO COTTON BOLLS. 
number of intervening calendar days has been taken as the basis and 
the additional periods approximated by a plan which has been fol- 
lowed throughout and which is believed to have produced very 
nearly correct averages. To the number of intervening calendar days 
has been added the known additional hours and one-half the hours 
between observations during which egg-laying or hatching might 
have occurred. In many cases the exact time of the egg-deposition 
or of hatching was noted, consequently lessening the chances for 
error. For example, a female was observed in the act of depositing 
an egg-batch at 4 p. m., July 16. This batch had hatched when the 
record was taken at 3 p. m. on July 23. The number of intervening 
calendar days in this case was six. The known additional period is 
8 hours, 4 p. m., July 16, to 12 midnight. The period preceding the 
time the eggs were first noted as having hatched, during which no 
observations were made, was 23 hours, one-half of which is added to 
the known period of 8 hours, making practically five-sixths of «a day. 
This added to the intervening calendar days gives 6f days as the 
approximate incubation period. 
Table XIV. — Relation of temperature to period of incubation of eggs of the conchuela. 
Period. 
Num- 
ber of 
egg 
batches. 
Num- 
ber of 
eggs. 
Range. 
Average. 
Place. 
Inter- 
vening 
calen- 
dar 
days. 
Approxi- 
mate in- 
cubation 
period. 
Average 
daily mean 
temperature 
for interven- 
ing days. 
Daily 
mean 
tem- 
pera- 
ture. 
Approxi- 
mate incuba- 
tion period. 
Tlahualilo, Du- 
rango, Mexico. 
Do 
1905. 
July 14-23 
July 22-30 
Aug. 6-Sept.l5-. 
Sept.l6-Oct.5... 
Julyl4-Oct.5... 
3 
5 
11 
7 
99 
234 
350 
313 
6 to 6 
5 to 4 
3 to 2 
6 to 4 
Days. 
7i to 6§ 
6ts to 5^ 
44 to 34 
7 to 5 
°F. 
75. 4 to 76. 1 
79. 1 to 79. 5 
80. 1 to 86 
73.7 to 75 
°F. 
75.8 
79.4 
82.8 
74.3 
Bays. 
6 
5 
3 
5 
Hours. 
19 
9 
Dallas, Tex 
Do 
15 
23 
Summary with 
averages 
26 
996 
2 to 6 
34 to 74 
73.7 to 86 
78 
5 
8 
From the last three columns of the above table can be computed 
the average effect of 1° of temperature on the duration of the 
incubation period within the limits noted. 
Table XV. — Effect of 1° of temperature on incubation period of eggs of the conchuela. 
Place. 
Range, average 
daily mean 
temperature. 
Number of 
degrees 
represented 
by range. 
Increase or decrease in incu- 
bation period correspond- 
ing to 1° of temperature. 
Tlahualilo, Durango, Mexico 
75. 8 to 79. 4 
74. 3 to 82. 8 
3.6 
8.3 
0. 39 days or 9 hrs. 30 min. 
Dallas, Tex 
. 27 days or 6 hrs. 30 min. 
The average of the Tlahualilo and Dallas records shows that between 
the limits of 74.3° and 82.8° the average increase or decrease in the 
incubation period corresponding to a single degree of temperature is 
