observed in Bombyx Cynthia. — - 487 
rule expect the male to emerge first, there must be frequent ex- 
ceptions, as, for instance, a half-starved female would precede a 
well-developed male, a stunted second brood would run a race 
with a full-fed first brood, and this will, to a certain extent, ex- 
plain the difference in observations made on the same species by 
different observers, 
This point, priority of appearance, is of considerable conse-’ 
quence in the culture of silkworms: the cultivators of Bombyx 
Mori use every endeavour to obtain the different moults and 
changes passed by all their stock on the same day. Hence if any 
linger behind they are thrown away, if any precede the others 
they are also got rid of; though it is confessed that they are the 
strongest and most vigorous worms. Hence as a result of this 
interference the cocoons are all spun up together, and the moths 
emerge on the same day; but this is the result of domestication 
and human manipulation, and the habit has been artificially in- 
duced by rejecting all those individuals that will not conform to 
it; but the same uniformity is net observed in the wild races. 
Thus in the case of Bombyx Yamamai, we find M. Personnat, in 
his book on that species, writing that the habit of the Yamamai is 
for the males to precede the females, so that males at the begin- 
ning of the season and females at the end are lost from want of 
mates. ‘To prevent this, itis desirable to retard those which first 
change to pupz, and to hasten the later ones, so as to equalize the 
interval ; this is effected by placing the first cocoons in a cool, 
and the later ones in a warm place. M.Chavannes recommends 
only to retard the males, which have a propensity to emerge first: 
taking 100 cocoons and weighing them and dividing by 100 he 
ascertains the mean weight of a single cocoon; those that exceed 
the mean weight are females, those that fall short of it are males. 
Elsewhere M. Personnat declares that he can separate the male 
from the female larve after the last moult, by observing those 
which grow the fastest and eat the most; these he declares are 
males, and will spin up first; he proposes to retard these by giving 
them a somewhat scantier diet, and to hasten the others by supply- 
ing them with an abundance of fresh food ; and thus he expects to 
equalize the time of spinning. 
Now with regard to B. Cynthia, it must be borne in mind, that 
of the cocoons gathered in any year some at least give their moths 
in the autumn of the same year; these then are the earliest born 
of the brood. My first experience in the autumn of 1863 was with 
about twenty pupz of B. Cynthia ; of these two larve had been 
