NOTES ON DANAID BUTTERFLIES — CLARK 535 



than by the annual mass incursion of immigrants from the south. 

 Wliile it is possible that a few individuals may succeed in over- 

 wintering in the north, as occasionally happens in the case of Phoehis 

 eubitle^ it seems most probable that most of the northern population 

 each season is derived from individuals of southern origin, as is 

 usually assumed. 



Dr. Frank Morton Jones, of Wilmington, Del., and Miss Dorothy 

 K. Cleaveland, of California, Pa., have both been so kind as to send 

 me records of unusual interest in connection with the northward 

 migration. 



Dr. Jones writes that at Virginia Beach, Va., from April 18 to 30, 

 1906, throughout most days, one to three or four of these butterflies 

 were usually in sight, flying north or northwest, some obviously 

 seeking the larval food plant. There were many dead ones along 

 the shore, washed up by the waves. 



This note is particularly interesting and significant in view of 

 the fact that later in the season, in summer and autumn, this is not 

 a common insect about Virginia Beach. It also suggests an explana- 

 tion for the occurrence of the form with white preapical spots on 

 the fore wings {megalippe) in southeastern Virginia. Individuals 

 of this form, which so far as known is normally nonmigratory, may 

 join the flocks of plexipjms in the far south where both occur. 



Miss Cleaveland thus describes a flight presumably of this species 

 seen at Tahiequah, Oklahoma, on March 9, 1928 : 



Tonight about 5:30 I saw a flock of hundreds of butterflies (?monarchs) 

 flying low over my head, due north, characteristic butterfly flutter-flying and 

 near enough to see the lacli of bodies like birds, but too far to see markings. 

 I was on upper Delaware Street, just starting to supper from the Rosses'. 



This is the note, made at the time, in my bird (and other nature subjects) 

 journal. From all appearances I felt confident at the time, and have ever since, 

 that I saw a northward spring migratory flight of monarch butterflies. It was 

 much smaller than fall flights I have seen, but otherwise similar. The creatures 

 were too close to me and I am too familiar in observing nature to be mistaken 

 in their identity as butterflies. I judged they were monarchs because of their 

 relative size and because I have seen the monarch southward flights and know 

 something of their habits. 



Dr. Carroll M. Williams writes that in the fall of 1936 he noticed a 

 southerly movement of this species at Richmond, Va. "The steady, 

 yet completely scattered migration in a general southern direction 

 was quite apparent. No hint of mass migration was visible, however." 



Dr. Williams quotes from a letter from Mrs. Walton, of Clifton 

 Forge, Va., describing a mass migration in that locality. Mrs. 

 Walton wrote: 



During the first of October 1935 a great mass of monarch butterflies passed 

 through the valley coming from the northeast and following the valley river 

 [the James] and railroad. They were about 30 yards in width and 6 feet in 



