878 Journal of Agricultural Research vol. vi, no. 23 



and the moths were seen to be apparently feeding on the nectar. In the 

 field during the same period the moths were seen to pause in their flight 

 from field to field and visit blossoms of such plants as mustard and clover. 

 The various lots of eggs were allowed to hatch and the larvae were 

 reared in the greenhouse during the winter. Critical notes on instars 

 and stadia were also made for later publication. 



DURATION OF THE EGG-LAYING PERIOD 



It is not probable that the writer observed the very beginning of the 

 egg-laying period when, on September 30, the first moths were seen to be 

 laying. It is altogether probable that the period began some days earlier, 

 and there is no absolute evidence that egg laying had not been in progress 

 for some weeks. It is quite clear, however, that the period closed about 

 October 14, when a cold spell with rain occurred. When the weather 

 cleared again, observations were resumed in the fields, but only a few 

 scattering moths could be found, even though the temperature was 

 favorable. October 8 was noted as the date on which the maximum 

 activity of moths and egg laying was observed, and some eggs were laid 

 as late as October 12. It may be safely stated that the egg-laying period 

 is two weeks or more in duration. 



NUMBER OF EGGS LAID 



A detailed record of the number of eggs laid by individual moths was 

 not made, as several circumstances in connection with the methods used 

 interposed to make this difficult. The writer was influenced also by the 

 fact that the moths had laid a part of their full number of eggs before 

 being confined, which made it impossible to get complete data. The 

 largest number actually counted was 252, all laid during one night, but 

 this probably falls considerably below the actual maximum number. 

 From this the number varies down to a very few, which may be accounted 

 for in part by the moths having laid eggs in the field before being captured. 

 The moth that laid 252 eggs died soon after and was dissected, the 

 ovaries showing many immature ova. 



DURATION OF THE INCUBATION PERIOD 



The writer has complete records of the duration of incubation in 23 

 lots of eggs. A part of these were kept in the insectary and a part in 

 an outdoor shelter. The minimum period recorded is 9 days, the maxi- 

 mum 21 days, and the average 16.77 days. The wide variation shown 

 is striking and can probably be explained. The egg lots were kept dur- 

 ing incubation in small tin boxes which were opened and examined daily. 

 It was observed that many eggs were badly shrunken, and the dark 

 embryos could be seen through the chorion. It was decided to add a 

 very small amount of water to each box, as it was feared that the eggs 

 would die from dryness. Accordingly, 1 to 3 drops of water were placed 



