1971] 
Alcock — Behavior of Stinkbug 
219 
and Horn, 1969). I offered sixteen juvenile redwinged blackbirds 
(Agelaius phoeniceus) two live E. conspersus adults. Nine of the 
birds ate both bugs, although usually not before giving behavioral 
signs that they found the insects distasteful (Alcock, ms. submitted). 
Stinkbugs, as is well-known, possess thoracic glands which are 
capable of secreting a volatile substance with an odor somewhat to 
extremely offensive depending on the species of bug and human tester. 
E. conspersus readily discharged its glands when handled roughly, or 
pecked by a bird, and several times I detected the odor coming from 
bugs trapped in a spider’s web. This action may protect some bugs 
from some predators, particularly birds, which are not strongly mo- 
tivated to feed. However, the insect is not solely dependent upon 
its secretion as it engages in a variety of defensive maneuvers — re- 
maining immobile much of the time, scuttling under leaves or drop- 
ping from them to the ground when approached or touched, kicking 
at ants, buzz-flying and wing-whirring. The defensive function of 
the latter two behaviors is purely speculative. However, bugs flying 
some distance definitely produced a fairly loud and, to this observer 
at least, a very bee-like buzz which might deter some aerial predators 
from attacking. Wing-whirring consisted of lifting and rapidly 
vibrating the wings, producing a loud buzz. Five of a group of about 
fifty bugs which I picked up, handled, and returned to a leaf remained 
on the leaf and wing-whirred. Similar behavior has been reported 
for some species of stinkbugs occurring on cocoa plants (Callan, 
1944) and might serve to startle or to warn a predator not to attack. 
Reproductive Behavior 
Only one generation of stinkbugs mated in Seattle although in 
California some populations have two reproductively active genera- 
tions in a single summer (Borden, Madsen and Retan, 1952). The 
adults which overwintered in leaf litter beneath the blackberries had 
emerged in large numbers by the time observations were begun (mid- 
May). Many adults and mated pairs were seen in the lot through 
late June but by the end of the first week in July very few adults 
could be found. By late July the second generation bugs were appear- 
ing in abundance with many feeding on the blackberries which were 
just beginning to ripen at that time. 
Mated pairs were rarely seen in the morning, never at midday, 
and often from 15.00 to dusk (21.00). I believe that the initiation 
of courtship and copulation occurred almost exclusively in the late 
afternoon and early evening. The mated pairs seen in the morning 
probably had coupled the previous evening. Hunter and Leigh 
