1924J 
Sex of Adult Cecidomyidoe {Oligarces sp.) 
151 
Thus in the eighth generation of material originally taken from 
a single colony in nature, and maintained in the Laboratory 
by the means already described, individual 4XX was segregated 
and transferred to a fresh culture made of the standard medium. 
In the third filial generation pupae and adults appeared as a 
result of crowding in the previous generation (F 2 ). All of these 
pupae and adults, 38 in number, which were sexed were females. 
In the fifth filial generation of the same strain, pupae and adults 
again appeared under similar conditions, in three separate 
cultures. In culture M222, 26 pupae and adults were sexed. 
All were females. This was equally true for the 23 individuals 
sexed in culture M223, and for the 59 individuals sexed in 
culture M224. Thus all of the 108 F 5 pupae and adults which 
were sexed were females. It is apparent that the progenitor of 
this strain, individual 4XX, must have beld)nged to a female- 
producing strain, since all of the pupae and adults produced by 
her offspring, both in the F 3 and F 5 generations, were females. 
Conversely, at the same time, and under similar conditions, 
individuals of other strains of known paedogenetic origin, gave 
rise to male pupae and imagines only. Thus in culture MN320 
5 pupae appeared; all were males. Similarly in culture CO 23 
five adults arose from an isolated paedogenetic mother of known 
paedogenetic origin. These five adults were males. 
Male pupae of Miastor rnetraloas appeared in a colony, 
maintained in decayed birch, wood in the laboratory in Paris 
(Prof. Maurice Caullery, Director) under crowded conditions 
in a tin box. Though these did not arise from larvae all of which 
had been carefully segregated and examined, the fact that they 
appeared some two months after the material had been trans- 
ferred to the laboratory makes it more than probable that they 
were produced by larvae which had arisen paedogenetically from 
paedogenetic larvae originally present in the material. This 
conclusion is further supported by the fact that all paedogenetic 
larvae which were examined and segregated reproduced paedo- 
genetically under similar conditions, about 2 weeks after birth. 
This would allow for four laboratory paedogenetic generations 
before the appearance of the male pupae. 
