40 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 
This would seem to be the natural result of the insects being fre- 
quently exposed to direct sunlight. The average daily mean tem- 
perature during July at Tlahualilo was 81.5° F., and during August 
at Dallas was 82.8° F., the daily mean for the 2 months averaging 
82.1° F. There is considerable variation independent of tempera- 
ture. This is shown by specimens reared from the same egg-batch 
and kept in the same cage, having in every respect equally favorable 
opportunities for development. The range in duration of the stages 
becomes greater with each succeeding instar, which fact is well 
brought out by Table XVI. 
Cold as a factor in retarding development. — At an average daily mean 
temperature of 69.4° F., the minimum length of the second instar 
among three specimens of the conchuela was 19 days, the period being 
from September 26 to October 15. In Table XVI is included a record 
of 7 days as the duration of this instar in one specimen. This repre- 
sented the minimum length of the second instar among more than 
10 specimens of the same brood. The period extended from July 20 
to July 27, .the average daily mean temperature being 77.9° F. A 
comparison of these two records plainly shows the effect of tem- 
perature on the duration of nymphal stages. Still greater retarda- 
tion was exhibited by a lot of 31 fifth-instar nymphs of the conchuela, 
although the records are not as exact as those given, owing to the 
fact that the specimens were collected in the field and the entire length 
of the stage is consequently unknown. The specimens referred to 
were collected at Barstow, Tex., on October 13, and taken to the 
laboratory at Dallas, where they were confined in a wire breeding- 
cage out of doors, and supplied with fresh cotton bolls up to about 
the middle of November. From among these nymphs adults appeared 
on the following dates: October 17, 2; October 18, 1; October 19, 2; 
October 26, 3; November 3, 1. Nymphs were recorded as dead on 
the following dates: October 10, 5; October 14, 2; October 16, 1; 
October 26, 1. On December 19, 2 nymphs were still alive, although 
feeble and barely able to crawl, owing to lack of food. The average 
mean temperature at Dallas from October 15 to December 19 was 
53.7° F., the October average being 62.9° F., November, 57.1° F., 
and up to December 19, 41° F. 
LENGTH OP LIFE WITHOUT FOOD. 
Like the adults, the nymphs of the conchuela, when deprived of 
food during the summer months, are short-lived. Nymphs in the 
first instar have been recorded as surviving as long as 5 days without 
food, which period is the longest ever noted under natural tempera- 
ture conditions in any instance during the months of July, August, 
and September. On August 11, 46 nymphs hatched from a batch of 
eggs and all but 3 of these were dead from starvation on August 14, 
