2 I 6 
Psyche 
[December 
t 
TIME 
Fig. 1. The number of stinkbugs counted on leaves (solid line) and on 
stems and berries (broken line) on a strip of blackberry bushes at various 
times during the day on 5 October 1971. The arrow points to the time of 
appearance of the sun following a period of early morning fog. 
Results 
Basking Behavior 
My attention was drawn to the bugs initially because so many 
could be found standing conspicuously on the upper surfaces of black- 
berry leaves in the full sun, particularly in the morning. These in- 
sects do not feed on leaves. 
As Fig. i illustrates with a single day’s census, the stinkbugs were 
rarely found on leaves until the sun had appeared in the morning. 
Then a very substantial proportion of the population of bugs moved 
quickly to places where they were fully exposed to the sun’s rays 
(Fig. 2). Dark green blackberry leaves provide a flat heat-absorptive 
surface for basking. Bugs tended to flatten themselves against the 
leaf on which they stood. They often chose leaves which were slanted 
upwards so that the bug’s brown back was oriented more or less at 
right angles to the sun. And, particularly in the early morning and 
late afternoon, when the sun was low, some bugs tilted their bodies 
