1977] 
Kanz — Monarch Butterfly Orientation 
123 
as soon as ambient temperatures permitted flight (approximately 
13°C) and engaged in feeding and mating throughout the day until 
sunset. 
Fall migrating Monarchs passing through Gloucester, Massa- 
chusetts, frequently remained in the area for several days, depend- 
ing upon weather conditions. Fall migrants left overnight roosting 
trees to feed (except when it rained) when ambient temperatures 
exceeded 10°-12°C (Kanz, 1973); mating occurred infrequently. 
At approximately 1600 hrs (EST) the butterflies returned to their 
roosting trees. This cycle was repeated each day until migration 
resumed. Fall migratory flights occurred between 1000 and 1400 
hrs, EST (Brower, personal communication; Urquhart, personal 
comminication). Fall migratory flight occurred with north, north- 
east, or northwest winds. 
Butterfly Orientation in Opaque Periphery Cages 
Laboratory-reared, non-migrants oriented toward the sun’s azi- 
muth throughout the day when the sun was the only environmental 
cue available (Fig. 1). To examine the possibility that this orienta- 
tion was actually a shade-seeking response (i.e., orienting to the 
shaded area of the cage and thus the side toward the sun) a sun- 
shade was positioned so that a shadow was cast over the half of 
the orientation cage facing the sun. If butterflies were seeking 
shade, their cage positions should fall within the shaded area of 
the cage. If Monarchs were sun-orienting, the butterflies would 
move toward the sun’s azimuth, stopping as they entered the shaded 
portion of the cage and their cage positions would fall along the 
shade line cast by the sun-shade. For such an experiment, 59% of 
the butterflies’ cage positions were within ± 5 cm of the shade line; 
and 72% of the cage positions were on the lid. Therefore, sunward 
orientation of caged, summer, non-migrants seemed to be an orien- 
tation to the sun and not an attempt to seek shade. 
Without celestial or terrestrial cues (overcast day), laboratory- 
reared, summer, non-migrants displayed a random orientation pat- 
tern (Fig. 2). With the sun visible, the mean absolute difference 
between a given 6 and the sun’s azimuth for that 6 (i.e., 1 0-sun 
azimuth | ) was 23° for opaque periphery cage, laboratory-reared, 
non-migrants, and 99° without the sun visible (Table I). Seventy- 
three percent of the sun-visible readings, versus 2% of the no-sun 
readings, showed significantly different Monarch cage distributions 
