50 



tion in oviposition was at once apparent. Following are the oviposi- 

 tion records for each night, the time of fertilization being marked by 

 the separating vertical line. 



Table XIII. — Effect of fertilization on egg laying. 





Infertile eggs. 



Fertile eggs. 



Moth No. 1 



41 50 



45 



3 



209 



35 



4 



180 



23 



7 



293 



894 



337 



1,570 



71 

 122 

 619 



227 



27 



200 



150 



7 



26 

 40 



36 

 20 



33 



34 



17 



^ 



Moth No. 2 





Moth No. 3 



31 





























CHANGES IN EXTERNAL APPEARANCE. . 



The original uniform white color of the egg persists for a period of 

 about fifteen hours. At the end of this time the upper third has 

 usuall}^ acquired a tint which is noticeably more yellowish than the 

 rest of the egg. The lower part of this yellowish portion gradually 

 darkens until, about thirty hours after the egg is laid, it has become 

 reddish or brownish. This brownish color deepens until, at the end 

 of thirty-six hours, it is quite distinct, even to the naked eye. The 

 outlines of the band are often broken or irregular and an additional 

 reddish spot, much less evident than the band, can now usuall}^ be 

 seen near the micropyle. When about forty hours have elapsed, the 

 whole egg has acquired a dull appearance, and the pigmentation of the 

 brownish band is also a little deeper. After this the whole egg rapidly 

 becomes dusky four or ^ve hours before hatching and the brown zone 

 is obscured. 



EMBRYONIC DEVELOPMENT. 



In order to connect the real development of the egg with the series 

 of external changes indicating its growth, it may be well to summarize 

 brieflj^ the embryonic development. 



The egg is fertilized shortly before it is laid and development begins 

 immediately. After about twelve hours the blastoderm is completely 

 formed and the beginning of the germ band several hours later causes 

 the appearance of the pale brownish ring when the egg is from fifteen 

 to eighteen hours old. The development of the embryo and the for- 

 mation of the appendages during the next twenty-four hours are indi- 

 cated by the deepening of the color. FinalW, the disposition of the 

 pigment in the chitinous skin and tubercles causes the blackening of 

 the egg just previous to hatching. 



HATCHING. 



The head of the fully developed embryo larva is quite plainly to be 

 seen through the eggshell, as is also more or less of the coiled body. 

 The head is now directly under the micropyle, and the body of the 

 larva extends backward with its dorsal surface pressed against the egg- 



