THE ORIENTATION OF MIGRANT AND NON-MIGRANT 
MONARCH BUTTERFLIES, DANAUS PLEXIPPUS (L.) 
By James E. Kanz* 
Department of Biology 
Tufts University 
Medford, Massachusetts 02155 
Introduction 
Many species of butterflies migrate (Nielsen and Nielsen, 1952; 
Tilden, 1962; Williams, 1951, 1958). The fall southward migration 
of the North American Monarch butterfly, Danaus plexippus L., 
is a classic example of long-distance insect migration (Urquhart, 
1960, 1976; Walker, 1914; Williams, Cockbill, Gibbs, and Downes, 
1942). Evidence from tagging studies indicates that the same but- 
terflies traveling south in the fall return northward the following 
spring (Urquhart, personal communication). It is unlikely, how- 
ever, that fall migrants from the northern latitudes (48° N) return 
as far north in the spring. 
Johnson (1969), Urquhart (1960), Williams et al. (1942), and 
Williams (1958) have provided descriptive information on several 
aspects of D. plexippus migration. However, little experimental 
work exists on the isolation of environmental orientation cues and 
their role in the seasonal movements of the Monarch. Baker (1968a) 
hypothesized an evolutionary scheme for the development of sun- 
orientation in a butterfly’s search for new habitats. Using field data 
on general flight directions of migrating European butterflies, Baker 
( 1968a, b) determined that sun orientation was apparently used by 
Pieris rapae, P. brassieae, P. napi, Maniola jurtina, Aglis urticae, 
and Inaehis io during their migrations. This paper reports which 
environmental orientation cues are used by caged migrant and non- 
migrant Monarchs, and suggests how such cues are used. 
♦Present address: Marine Biomedical Institute, University of Texas Medical 
Branch, 200 University Boulevard, Galveston, Texas 77550. 
Manuscript received by the editor August 20, 1977. 
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