136 
Psyche 
[December 
movements of countless butterflies can be explained, and it 
is to be hoped that intelligent efforts will be made to solve 
the problem of butterfly migration. 
Summary 
1. A southward migratory flight of Catopsilia euhule 
Linn, was observed in St. Louis County, Missouri, during 
September and early October, 1932. 
2. Wind and obstacles did not change the direction of 
the movement. There was no mating, or formation of 
aggregations, and no other species accompanied them. 
3. It is shown that although migration in this species 
may be related to environmental factors, or to internal and 
possible sexual conditions, yet the actual flight is due to 
voluntary efforts on the part of the butterflies. 
4. No return flight has been observed; repopulation is 
effected by means of the gradual northward spread of stray 
individuals, or through the increase in numbers of the few 
that survive the winter in the north. 
References 
Brower, A. E. 1930. A list of the butterflies of the 
Ozark region in Missouri. Ent. News, 41: 286-289. 
Calkins, Virgil F. 1932. The rhopalocerous Lepidoptera 
of Scott County, Kansas. Ent. News, 43: 210-215. 
Clark, Austin H. 1932. The butterflies of the District of 
Columbia and vicinity. U. S. Nat. Mus., Bull. 157 
(see pp. 52-57 for observations on migration). 
Heape, Walter. 1931. Emigration, migration, and nomad- 
ism. Cambridge, England. 
O’Byrne, Harold. 1932. Notes on butterfly migration. 
Bull. Brooklyn Ent. Soc., 27: 185-188. 
Scudder, S. H. 1899. Everyday butterflies. 
Williams, C. B. 1926. Voluntary or involuntary migra- 
tion of butterflies. The Entomologist, 59: 281-288. 
1930-a. The migration of butterflies. 
Edinburgh. 
1930-b. Collected records relating to 
insect migration: second series. Trans. Ent. Soc. 
London, 78: 139-170. 
