198 PHIL RAU AND NELLIE RAU 
class of insects does not seem to be fully known, but in this mate- 
rial it is clearly evident. 
An explanation of this early male emergence was attempted by 
Darwin. ‘The cause of the difference between the males and 
females in the period of arrival at maturity is sufficiently obvious. 
Those males which annually first migrated into any country, or 
which in the spring were first ready to breed, or the most eager, 
would leave the largest number of offspring and these would tend 
to inherit similar instincts and constitutions.”’ 
This explanation is far from clear when we try to apply it to 
Saturniid material. A more probable explanation would be that 
the males emerge first merely because they do not require such 
a long period of development to mature their gonads. The 
female has a large number of ova to nourish, probably requires 
a greater amount of food in the larval stage and a greater period 
of pupation, and late emergence follows. 
But the item of interest is to find whether early emergence of 
the males is an adaptation, as Darwin seemed to think, for the 
benefit of the species. From the data of 1910 it seems that 
‘adaptation’ gives us males at one time, and when these are almost 
dead or too old to mate then a succession of females, many of 
which die without leaving issue owing to the lack of mates. To 
illustrate this let us say that with 101 good males and 104 females 
in 1910, 52 males (more than one half) could not be mated, and 
even though we called to aid some of the 69 stray males which were 
attracted to the laboratory, still it was possible to supply only 
65 of the females with mates. It would seem that for the benefit 
of the race both sexes should emerge at about the same time (since 
both are mature for mating at about the same age) in order to 
eliminate any expenditure of energy in finding each other, and 
to eliminate any possibility of a great proportion of the males 
and females dying without having mated, in spite of the fact that 
the sexes may be equal.18 
It was suggested that the early maturity of the male may be 
due to a shortened period of development. This is deserving of 
18 Tt may be that the males of one area migrate to another territory to accom- 
plish mating, but we have no proof to that effect. 
