18 
Psyche 
[March 
peatedly enter the wrong compartment. This was so com- 
mon throughout the season that a number of the wasps 
must have made the same error many times. I can only 
offer the explanation that the nests are never in such close 
proximity in nature, and that a return to within a few inches 
would normally bring a wasp to her nest. But in the hive, 
all compartments look alike, a nest odor (if any) is con- 
fused with the odor from adjacent nests, and a few inches 
error would send a wasp into the wrong compartment. 
Eventually, of course, the wasps would seek out their home 
nest. 
The continued intrusion of wasps into the wrong com- 
partments afforded excellent opportunities to observe the 
natural tolerance and animosity of the various species 
toward the intruders. The results are very similar to 
tolerance observations on Polistes (3). 
In one hive were two maculata nests and a weakened 
arenaria nest. In this hive a returning maculata worker 
would be set upon if she ventured into the arenaria compart- 
ment; similarly an arenaria intruder would be pursued in 
the maculata compartments. Members of one maculata 
colony were permitted to enter the compartment and to 
walk upon the nest of the other colony; they did not enter 
the nest of the other colony. As a result of removing work- 
ers from the arenaria colony, the remaining population 
could no longer protect itself and the intruding maculata 
workers soon learned to steal the arenaria larvae as food for 
their own brood. 
Two adjacent arenaria colonies in another hive permitted 
the same freedom of trespass on their nests as was de- 
scribed above for the two maculata colonies. 
In flight outside the hives all the species were on good 
terms. They caused no trouble by virtue of their prox- 
imity. 
To discover the outcome of a prolonged intrusion of one 
species in the compartment of another, I closed the escape 
aperture of an arenaria hive and placed a large maculata 
worker within the arenaria nest. Immediately the arenaria 
workers formed a circle about the intruder, always facing 
her and reminding me of the entourage of worker bees about 
their queen. As soon as the maculata moved toward the 
