130 
Psyche 
[June 
sun azimuth line 
TIME OF DAY IN HOURS (EST) 
Fig. 4. Orientation displayed by fall migrants in a transparent periphery cage 
on a clear day. In contrast to summer non-migrants, fall migrants continue to 
sun-orient in the presence of both sun and terrestrial cues. Readings beginning at 
1345 hrs (EST) were an artifact of a sudden ambient temperature drop. 
The results of summer Monarch releases with the sun visible 
showed that most vanishing azimuths appeared to be down-wind 
rather than toward the sun (Fig. 5). Only the releases of (c), (f) 
and (h) were significantly grouped about their respective mean 
orientation direction. Vanishing azimuths for summer non-mi- 
grants on overcast days were down-wind (Fig. 6). The distribution 
of releases in all but (c) were significant about their respective 6' s. 
The releases of (f), with only a light surface wind, appear to be in 
the direction of the sun’s azimuth even though the sun’s position 
was obscured by clouds. However, most of these butterflies flew 
at an altitude ^ 20 m and, therefore, likely encountered stronger 
winds. The vanishing directions of summer Monarchs, therefore, 
appeared more influenced by wind than by sun. Vanishing azimuths 
were more scattered with light winds (^ 5 mph or 8 km/ hr). Low 
flight enabled Monarchs to fly against head winds that exceeded 
10 mph (16 km/ hr). Thus, Monarch flight direction was greatly 
influenced by the wind but was not competely determined by wind 
direction. 
Figure 7 shows the patterns of vanishing azimuths for fall mi- 
grants when the sun was visible. All 20 distributions were signifi- 
cant about their respective 0’s. The vanishing azimuths generally 
corresponded to the direction in which the wind was blowing with 
the exception of (a), (m) and (t). The releases of (a) occurred from 
a site that was surrounded by water except to the west; Urquhart 
