178 
season; and that the eggs may hafch in from eighteen to twenty- 
one days after deposition, or an average of about twenty days*. 
The disappearance of the chinch-hug after a season of extraor¬ 
dinary abundance is most commonly attributed to the immediate 
effect of wet weather, and no general idea concerning its economy 
is more firmly fixed then the supposition that even ordinary sum¬ 
mer rains will destroy it outright Nevertheless, no precise in¬ 
vestigation of its ability to endure submergence has ever been re¬ 
ported, and this supposition is really based on superficial obser¬ 
vation. The results of our experiments on this point may be 
summed up as follows: 
Chinch-bugs just emerged from the egg will survive a complete 
immersion of one to three hours; young of the first molt, three 
to five hours; of the second molt, six to nine hours; and of the 
third molt (pupae) eight to thirteen hours. Adults of the sum¬ 
mer generation will live under water from twelve to twenty-two 
hours, and those of the fall generation have revived after thirty 
to fifty-four hours complete submergence. 
Chinch-bugs just emerged may live floating on the surface of 
water seven hours, while those of the second molt may revive 
after twenty-three hours. Bugs of the second molt have lived two 
and a half days under such conditions; those of the third molt 
(pupae), three and three fourths days; and adults, about fifteen 
days. Chinch-bugs have even molted while in this situation, the 
wings and crust of the adult hardening, as if the insect were free. 
In the first article of this report I have described experiments 
showing the fatal effect on chinch-bugs of exposure to the heat 
of the sun in the dry dust of furrows made as a check to their 
movements from one field to another. These experiments did 
not enable us, however, to discriminate the part of this effect due 
to the heat of the dust from the part due to its physical condi¬ 
tion. I consequently arranged a series of three laboratory experi¬ 
ments with chinch bugs in confinement, in one of which the bugs 
were kept without food in bottles otherwise empty, in another of 
which they were kept on moist earth, while in a third they were 
shut up in bottles of dry dust. All were placed in the shade at 
the normal temperature of the season. 
It was ascertained in this way that cool dry dust had a decided 
insecticide effect, bugs of the two youngest stages dying in it 
within twenty-four hours, but older ones living from one to six 
days, according to their age, while the other lots in confinement 
lived from eight days for the youngest to forty days for the 
longest-lived adults. 
The details of observation on which the foregoing general state¬ 
ments are based are given in the following personal report by 
Mr. Johnson: 
mr. Johnson’s report of experiments. 
Sir:—T he following is my report on some experiments with 
chinch-bugs made according to your direction during the season 
* In earlier experiments 1 have found eggs to hatch in fifteen days after they were deposited 
(see my Fifth Report, p. 44), and experiments made in my ofh;e during the year l'895 demonstrate- 
that the incubation period may vary from twelve to twenty-two days. 
