1935] 
Beetles Associated with Ants 
229 
the histerid remained passive with legs and antennae out- 
stretched. 
On the following day the histerid was discovered in the 
morning gnawing spasmodically on the dead ant’s left pos- 
terior leg at the femorotibial joint. Through the day this 
gnawing continued, and by 4:00 P.M. it had chewed free 
a small strand of the articular membrane and was persist- 
ently enlarging the perforation. 
This isolated account is typical of the beetle’s activities 
within the laboratory nests, and we conclude that the his- 
terid is thoroughly adjusted to the ulkei biocoenose, where 
it is attended, cleaned, fed upon regurgitated foods by the 
worker ants and also eats dead insects in the nest. The 
workers in return for these many attentions bestowed upon 
the histerids, seem greatly stimulated by the glandular 
pronotal areas. This species is the most perfectly adjusted 
to ulkei of any of the guests so far reported. 
Observation of these fifteen species of beetles associated 
with Formica ulkei show us that the several species eat 
many things and are in different categories with respect 
to food competition and adjustment to the host. The com- 
plexity of food interrelations for this very imperfectly un- 
derstood biocoenose is suggested by the diagram in the ac- 
companying figure (Fig. 1). 
Another problem involved is the ecological role played 
by each form in the nest. The position of a species is 
usually a definite one with respect to its relation with other 
nest inhabitants, although this status is frequently different 
in its several life history stages. Our grasp of many of 
the larger community problems may depend to an unknown 
degree upon the amount of accurate information we have 
on the smaller, microhabitats, and therefore a great deal 
of autecological data must be had before we can really 
understand a large unit. The following table (Table III) 
is a tentative arrangement to indicate the role of these 
fifteen forms in the ulkei nest, the technical terms follow- 
ing the system employed by Wasmann and later modified 
by Wheeler (1926). 
Since many of these species have a facultative role, and 
consequently occupy both the ulkei nest and other habitat 
niches, the complexity is greatly increased. These possible 
habitat interrelations are shown for some of the forms in 
Fig. 2. 
