274 THE CANADIAN ENTOMOLOGIST 



that each emerging female will ordinarily start sixty-eight larvae 

 on their perilous life cycles. 



The longest incubation period for any egg mass was found 

 to be 32 days, the shortest 23, with an average of 26 days. Un- 

 doubtedly, as is to be expected, temperature plays an important 

 role in the determination of this period, for eggs exposed to the 

 sun, on account of a crack in the window box, under the identical 

 conditions of others in other respects, hatched at least two or 

 three days before those better protected from its rays. 



The average number of days the females lived after being 

 taken was about nine, although individuals varied widely in this 

 respect. 



Considering now some of the suggestive results we find good 

 reasons for believing that the temperature prohibitive to the 

 emergence of females is between 20 and 25 F. During the first 

 four days of the experiment the average daily temperature re- 

 mained steadily below freezing, about 30 F., and females were 

 found in abundance, but during the fifth night the temperature 

 dropped to 18 and as a result it was impossible to secure the 

 moths either the next day or the following, which was preceded 

 by a night even colder, but on the third day thereafter, following a 

 decided rise in temperature during the previous day and night, 

 plenty of moths were taken. The temperature of the fifth night 

 was assumed to be that critical to the emergence of the. females. 



A study of Plate II shows no eggs hatching on April 1st, 

 4th, 7th, 8th and loth at temperatures of 38, 40, 36, 39^2 and 46 

 degrees respectively, but on the other hand on April 2nd, 5th, 

 12th, 13th and 14th they are shown to have hatched at tempera- 

 tures as low as 48)^, 50, 49, 49^^ and 483^^ degrees. Based upon 

 the above figures an average daily temperature around 45 F. 

 might be considered as that fatal to the hatching of eggs in the 

 ordinary run of weather. 



The count made upon the males and females emerging under 

 a single light-tight box, 17 x 253^^ inches in area, showed 34 males 

 and 11 females, or approximately 75% of the whole number were 

 of the winged sex. 



On March 20th aside from the usual 100 normal females, 25 

 were taken from the tanglefoot bands, each having a certxiin amount 



