1923] Occurrence, Life-Cycle, and Maintenance of Miastor 101 
harden. For mass cultures of psedogenetic larvae I have found 
petri dishes very suitable for culture containers. Since they 
allow but little loss by evaporation, the water of condensation 
falling back upon the culture medium, the medium remains moist, 
suitable for the reproduction of the yeast and the growth of the 
larvae for some time. Larvae may be more easily removed for 
examination from cultures reared in petri dishes than from those 
maintained in deep containers. Very small petri dishes may 
be used for individual cultures. 
After the agar has hardened, a little powdered yeast is 
sprinkled over its surface, to which the larvae are transferred. 
Cultures are then placed in the incubator at 20-22 degrees 
Centrigrade. 
I have employed this culture medium for Miastor larvae of 
various species, and have observed in colonies reared in this 
way all the larval forms occurring under natural conditions. 
It seems then that a method has been found for rearing 
cultures of Miastor larvae in the laboratory under conditions 
which may be easily regulated. This method should be suit- 
able for maintaining cultures of a paedogenetic insect in the lab- 
oratory for class work as well as for carrying on investigations 
concerning the factors influencing the life-cycle and the poly- 
morphism of the larvae of Miastor. 
