POLYGAINIY. 343 



Fertilization Experiment. 



To determine the length of time necessary for fertilization, 

 twenty-five virgin females were exposed in infested localities. 

 After mating had commenced, the males were removed at 

 the end of given periods of time, varying from one minute 

 to one hour ; the females were placed in boxes, and allowed 

 to deposit their eggs. 



In all cases where the male was removed before six 

 minutes, the eggs proved infertile ; but where they were 

 allowed to remain beyond that time, the eggs were fertile. 



Polygamy. 



As a rule, the males of this species mate with but one 

 female, or with two at the most, but instances have been 

 recorded where single males mated with six females, and 

 five other males mated with three females each. Polygamy 

 is exceptional among the females. In August, 1894, a 

 female moth, at the insectary, mated with three males ; but 

 nearly all females reared in confinement, as well as those 

 whose mating has been observed in the field, paired with 

 but a single male. 



The fact that a male imago may fertilize several females 

 has a practical bearing on the work of destroying the gypsy 

 moth. It would seem to indicate that the destruction of the 

 males, either through natural or artificial agencies, is of but 

 little importance. 



Length of Life of Imago. 



The maximum numl)er of days of the life of thirty-four 

 females which had not mated was found to be 10, the mini- 

 mum 1, and the average 6.15 days. The maximum number 

 of days of the life of forty-two females which mated was 

 found to be 12, the minimum 1, and the average 7.69 days. 

 The actual length of life of the male moth is hard to deter- 

 mine, as they probably live much longer when free than when 

 kept in confinement. Five males which had not mated lived 

 respectively 6, 7, 8, 11 and 8 days. 



