1977] 
Kanz — Monarch Butterfly Orientation 
121 
Materials and Methods 
Experiments used laboratory-reared and “wild-caught” Monarch 
butterflies ( D . plexippus L.) of both sexes. The laboratory colony 
was reared from the egg under mid-summer conditions: 24° C under 
a 15:9 hour light/ dark schedule (Kanz, 1973; Urquhart and Stegner, 
1966). Some laboratory-reared Monarchs were reared under a 
photoperiod advanced 6 hours. Predominantly laboratory-reared 
animals were used for summer experiments. Wild-caught migrants 
were used in fall tests. Fall migrants were maintained in the field 
in frame cages (3 X 3 X 2*4 m) covered with nylon netting and placed 
over patches of golden rod and asters. 
Summer experiments with non-migrants were conducted in an 
open field in Lexington, Massachusetts. Studies with fall migrants 
were conducted at the Eastern Point Audubon Sanctuary in Glouces- 
ter, Massachusetts. Eastern Standard Time (EST) was used for 
summer and fall experiments. 
Experimental orientation cages were circular (80 cm diameter) 
and mounted on a rotatable base. The floor of the cages was 
marked off into 45° sectors. The periphery (20 cm height) and 
top were wire screening. Entrance was through a door in the top. 
Two types of orientation cages were used: (1) transparent-periphery 
cages with both terrestrial and celestrial cues visible and (2) opaque- 
periphery cages with a beige strip of no-glare cloth around the 
periphery so only celestial cues were visible. 
Experiments were conducted under sky conditions ranging from 
clear to overcast. Orientation cages were placed in the center of a 
field so that terrestrial cues were symmetrical about the cages. Ter- 
restrial cues were distant enough so as not to be visible to animals 
in opaque-periphery cages. Cages were oriented to true north and 
the cages could be rotated to any desired azimuth. 
Male or female Monarch butterflies (N = 10-20) were released 
into an orientation cage, and data collection started 15 min later. 
Cage positions of the Monarchs were monitored at intervals rang- 
ing from 1 to 15 min and positions were scored on circular data 
sheets divided into 45° sectors. Each animal’s position in relation 
to true north could be designated within ± 5° . With few exceptions, 
the cage position recorded for each animal was a resting position 
(i.e., the butterfly was not in flight). Following each reading, the 
cage was usually rotated. The side of the cage from which the 
