226 
Psyche 
[December 
The Formation of Aggregations 
Groups of stinkbugs, both adults and nymphs, are quite well-known 
(Thomas, 1954; Southwood and Le:ton, 1959; Canerday, 1965) 
and appear to have multiple functions. First, mating aggregations 
permit males to locate or attract females of their own species (Tey- 
rovsky, 1949; Southwood and Leston, 1959). The means by which 
reproductively active E. conspersus manage to form groups is un- 
known. The fact that non-reproductive individuals also clump to- 
gether means that specific sex pheromones are not a necessary basis 
for group formation. 
Second, clumping could be an anti-predator adaptation. A group 
of toxic, warningly-colored insects may more effectively advertize po- 
tential unpalatability than scattered individuals could. In addition 
should one member of a group be taken, the predator would be likely 
to avoid the others. However, the formation of groups by nymphs 
and adults of a cryptically colored species such as E. conspersus can 
hardly serve this function. As previously noted, the bug proved to 
be edible, although apparently distasteful, to redwinged blackbirds. 
The formation of groups must make these bugs more vulnerable, not 
less, to hungry redwings as well as to their wasp predators which can 
probably learn to return repeatedly to a productive searching area 
(Evans, 1966). The fact that the bugs are not terribly nimble also 
places a premium on avoiding detection by their enemies. Thus there 
must be some other advantage for group formation by second genera- 
tion adults and nymphs which outweighs increased risk of attack by 
predators. What this advantage is remains uncertain. However, 
given the death of the ferns it seems probable that the bugs were 
injecting toxic substances into their foodplants as Hemiptera are 
known to do (Nuorteva, 1958; Adams and McAllen, 1968). The 
salivary glands of some mirids contain pectinases (Laurema and Nu- 
orteva, 1961) as does as least one lygaeid (Adams and McAllen, 
1958). The pentatomid D. baccarum possesses salivary proteases and 
amylases (Nuorteva, 1954). Thus it is possible that by feeding in 
groups individual bugs may extract plant juices more easily than 
otherwise. In any event, the relative advantages of group formation 
as opposed to dispersal must be rather closely balanced given the great 
variability in the tendency to aggregate exhibited by E. conspersus. 
Summary 
This paper describes the behavior of members of one population of 
Euschistus conspersus Uhler, a small brown stinkbug. These bugs 
characteristically bask for some time after sunrise, often on black- 
