THE CANADIAN ENTOMOLOGIST 273 



The relation of the duration of the egg stage to outdoor 

 temperatures is shown graphically in Fig. 11. The full line 

 temperature date curve was plotted by using the average daily 

 outdoor temperatures as ordinates and the dates as abscissae; the 

 broken line egg-stage-date of oviposition curve, by using the 

 incubation period as ordinates and dates of oviposition as abscissae. 

 On the same plate the parallel transverse lines represent the incu- 

 bation periods of eggs laid at different times during the season; 

 the left end indicating the date of oviposition and the right that 

 of hatching. 



Passing now to the consideration of results it seems best to- 

 discuss first the reasonably definite conclusions and later those 

 which might be termed suggestive. 



The females began to oviposit during the second night after 

 emergence from the ground, if we assume that most of the moths 

 collected each day emerged the evening of the preceding day. 

 Or, in other words, they began to oviposit during the first night 

 in captivity. The relative percentages of eggs laid during each 

 day following collection are: 1st, 32.93%; 2nd, 38.4%; 3rd, 15M%; 

 4th, 7%; during remaining period of life, 6.03%. It is interesting 

 to note that 71.33% of all eggs deposited appeared during the 

 first two nights after the moths were collected. 



The average number of eggs deposited by each female under 

 the conditions of the experiment was surprisingly low. The 

 17,681 milligrams of eggs deposited by 2,500 females means only 

 an average of 82.7 eggs apiece, which when contrasted with figures 

 running as high as 400 given by dissections as well as by standard 

 texts, seems hard to account for. In all probability the females of 

 this species, like those of many others among insects, normally 

 fail to deposit all the eggs of which they are capable or possibly 

 some sterile females die before leaving a single mass of eggs. 



Turning to the figures on the percentage of sterility of eggs 

 we find the following averages for all laid during the various nights 

 in captivity: 1st, 10.8%; 2nd, 11.2%; 3rd, 22.4%; 4th, 46.7%; 

 and thereafter, 82.8%, with a general average of 19.15% sterility. 

 Therefore, if the average females lay 82.7 eggs and 19.15% of these 

 are sterile we can say, disregarding all other casualty factors, 



