THE TRIBE OF THE CRESCENT-SPOTS 147 



larger than the spring form and it has very few markings 

 on the under surface of the hind wings. 



The Yearly History 



As it occurs in New England the yearly history of this 

 little butterfly runs something like this. The spring form 

 of the adult appears in May and lays eggs upon the aster 

 leaves. These eggs hatch into caterpillars that feed upon 

 the aster leaves for several weeks and then change to 

 chrysalids, remaining in the latter stage ten days or 

 two weeks. They then come from the chrysalids in the 

 form of the summer butterflies which begin to appear about 

 the middle of July and continue to emerge for at least a 

 month. These lay eggs upon the aster leaves again and 

 the Kttle caterpillars that hatch from them feed for a few 

 weeks or until about the last of September. They are 

 then only partially grown, but they make no attempt to 

 complete their transformation at this time. Instead they 

 drop to the ground and go into hibernation, remaining in 

 this condition until early the following spring. They then 

 begin feeding again and complete their development in 

 time to emerge as the spring form of the butterfly in May. 



Some very interesting experiments by William H. Ed- 

 wards have shown that the smaller, darker spring form of 

 the butterfly is due to cold. He placed upon ice chrysaHds 

 that would normally produce the summer form and found 

 that the specimens so treated produced the spring form. 



This butterfl}^ is one of the best known examples of the 

 variation in the yearly cycle due to differences in latitude. 

 This is readily shown by a brief summary of its life-his- 

 tory, from north to south. 



In the far northern climate of Labrador there is but one 



