When the caterpillars are full grown, they fall or crawl to the ground and scatter more or less in search of shelter. Each attaches itself to any protection it may have found and changes to a grayish or brownish chrysalis more or less angular. It remains in this condition for a period that varies greatly with the weather conditions, averaging about two weeks. There are two distinct forms of these butterflies which vary so greatly that they were once considered separate species. They are now known, however, to be only seasonal variations. In New England two broods of the insect occur, one in spring, the other in summer. The spring form is called technically _Phyciodes tharos tharos_. In this form the under surface of the hind wings is very distinctly marked with blackish spots. The summer form is called _Phyciodes tharos morpheus_. It is noticeably 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 little 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. Edwards have shown that the smaller, darker spring form of the butterfly is due to cold. He placed upon ice chrysalids that would normally produce the summer form and found that the specimens so treated produced the spring form. This butterfly 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-history, from north to south.