418 p. W. WHITING 



at any ordinary temperature or humidity, but the females are 

 very perverse about egg-laying. The proper conditions have 

 not yet been determined, and consequently the results obtained 

 have been a chance selection from a very large number of pairs 

 set. Usually not more than 5 or 10 per cent of the pairs prove 

 fertile, but I have occasionally had as good a ratio as 50, 60, or 

 even 70 per cent. The most frequent condition of infertility is 

 the failure of the female to oviposit. Examination has been 

 made of a large number of such females. The abdomens have 

 been found to be filled with large eggs apparently matm-e and 

 normal. Another peculiar condition is the failure of the eggs to 

 hatch unless almost all the eggs are laid. It has been found that 

 if the female retains a large proportion of her eggs, the eggs which 

 are laid do not hatch. The pairs have in this case frequently 

 been observed to mate, but it is possible, nevertheless, that the 

 eggs have not been fertilized. Records are being kept of all 

 these conditions and further studies will be made. 



If conditions are warm and humid, moths begin eclosing five 

 weeks after the parents have been isolated. Considerable vari- 

 ation obtains in rate of development of the larvae from any one 

 pair, so that moths of one fraternity are sometimes eclosing over 

 a period of one, two or even three months. It is probable that 

 this tends to compensate for the high sterility, for if conditions 

 are not favorable for oviposition at one time they may be at 

 another. There is thus no difficulty in keeping mass cultures. 

 Even extreme reduction in food with consequent reduction in 

 size of the moths does not exterminate them. Despite the 

 extreme sensitiveness of the adults, the species is adapted to 

 tide over very unfavorable conditions. 



Since mating takes place as soon as tlie wings are dry, females 

 are counted as virgin only when found in cultures before a male 

 has emerged. 



