24 
tain independently, as nearly as possible, the length of time from 
the appearance of the moths of one brood to the appearance of 
those of the following brood, or, in other words, the total length of 
life of the individual, which must be the sum of the various stages. 
As we have already touched upon the length of time the insect 
exists in the egg state, and have no further data to present, we 
shall proceed upon the assumption already made, that they remain 
in this state about two weeks. As a matter of course, we refer only 
to those broods that hatch out during the season in which they 
are deposited, leaving, for the present, the question as to whether 
they pass the winter in this form out of the question. 
Prof. Riley found, that by feeding the worms in confinement at 
an average temperature of 80°, some passed through the larval state 
in fifteen or sixteen days, and in his last article on this subject 
(1880) uses this in part as a basis on which to found his present 
theory as to the number of broods. But all the evidence I have 
been able to obtain in reference to this point shows that they con¬ 
tinue about a month in this state when in their natural condition. 
My experience in 1861, in the natural temperature of the locality, 
gave, as nearly as I could estimate the age of the worms at the 
time, twenty-eight days as the shortest period. Mr. Walsh, who 
also reared the species from the larval state, gives “from four to 
five weeks” as the length of the term. Dr. Packard allows one 
month. Dr. Fitch says they continue to feed and travel about three 
weeks from the time they are discovered, which he says is when 
they are about one-third grown. 
The investigations of these parties agree in fixing the average 
time at not less than one month. The dates at which the worms 
have been observed and the moths captured will be found, by a 
careful examination, to agree with this conclusion. This we will 
notice after we have called attention to the length of time the insect 
remains in the other states. 
The individuals of the Spring broood remain in the pupa state, 
as shown by repeated experiments, from two to three weeks. My 
experience gave an average of seventeen or eighteen days; Dr. Fitch 
says “nearly three weeks;” Dr. Packard and Prof. Riley say, “from 
two to three weeks;” Mr. Walsh’s specimens remained in this state 
fifteen days. I therefore assume seventeen days as the average 
time the insects of the Spring brood remain in this state. 
The moths reared by Prof. Riley commenced to lay about two 
weeks after issuing from the chrysalides. This is the only positive 
evidence we have on this point, but it agrees quite well with such 
data as we have in reference to their habits in their natural con¬ 
dition, and therefore may be taken as sufficiently accurate for all 
practical purposes. He adds that they continued to lay for two or 
three days. This will give an average of sixteen days from the time 
the moth issues until the eggs are deposited. 
The term of existence of the individual, from the time the egg is 
deposited until the resulting moth deposits is, therefore, on an 
average, seventy-seven days: egg 14, + larva 30, + pupa 17, + 
moth 16 = total 77 davs. 
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