150 
Psyche 
[J une- August 
I have previously reported (Harris 1923, 3, 1924, 1) that 
pupae and adults can be produced at will in the laboratory by 
maintaining a crowded condition in the previous generation. 
Pupae and adults produced in this way were used as material for 
the present study. These pupae and adults arose in all cases 
from paedogenetic stock, taken in nature, and maintained on 
artificial culture medium in the laboratory. In no case are 
data given on cultures which did not pass at least one paedo- 
genetic generation in the laboratory previous to the appearance 
of pupae-larvae. In some cases the data concern mass cultures, 
in other cases cultures which originated from an isolated paedo- 
genetic mother larva. 
It was found that the pupae and adults which appeared in 
mass cultures, made from paedogenetic larvae of paedogenetic 
origin, were as likely to be males as females. Thus in cultures 
Bi 2 and Ci 2 of 28 pKipae, chosen at random and sexed, 18 were 
males and 10 were females. In culture M79, of 2 adults, 1 was a 
male, 1 a female. A similar sex ratio was observed in culture 
MNO 340. 
All of these cultures were originally made of varying numbers 
of isolated paedogenetic larvae of known paedogenetic origin. Thus 
it is clear that male as well as female pupae and adults arise from 
larvae which have been produced by paedogenesis. Male pupae, 
when dissected, were found to contain large numbers of sperms 
in the gonads, while in the female usually about four or five 
large eggs are visible in living specimens. It seems likely then 
th^t both males and females are functionally as well as mor- 
phologically different. Up to the present time, however, I 
have not attempted to obtain progeny from adults, and so 
cannot state whether or not copulation can be easily obtained 
in the laboratory. 
Whether the number of males will be equal to or greater 
than the number of females, or vice versa, in a given culture, 
was shown to depend upon the type of stock which was selected 
in making the cultures, for it appears that in the same colony in 
nature certain paedogenetic larvae belong to male producing 
strains, \^^hile other larva) constitute female producing strains. 
