1929] 
Myrmecocoles of Formica ulkei 
203 
as well as at Palatine on August 6, the only trip made to 
the latter locality. 
This carabid appears to occupy a most fortunate position 
in the ulkei community. It is practically unmolested by the 
worker ants at all times, as mentioned before the beetles 
running in and out of the galleries at will, undisturbed by 
the ants, and occasionally becoming motionless when an ant 
passes them. The carabids were killed on several occasions 
and placed on the surface of the mounds at Palos Park, and 
the worker ants did not molest the beetles very much more 
when dead than when alive. Thus, although the ulkei were 
bringing in all sorts of insects, dead or alive, for consump- 
tion, the dead Tachyura would often be passed by a worker, 
occasionally investigated, and rarely picked up. In the latter 
case, the worker would shortly drop the beetle and walk 
away. This was also observed in laboratory nests of ulkei. 
On the other hand the larvae (Carabidae?) taken at 
Palos and at Palatine, when placed with ulkei workers, 
were pursued and one was devoured by the ants. 
Observation of Tachyura shows that, although unmo- 
lested by the other members of the ulkei community so far 
observed, the carabids prey at will on anything they can 
devour. In this they resemble the behavior of the hyaena, 
only attacking when their prey is dead or sufficiently dis- 
abled to be harmless, as the following points will indicate. 
In the first place, these carabids are essentially cannibal- 
istic, and given a dead or disabled incurva , it is seized by 
others if they are within a sufficiently short distance to 
be stimulated by the food. Apparently the beetles must be 
within several milimeters before the presence of food sti- 
mulates them, and if the latter is removed a short distance 
away they have difficulty in again locating it. If one of 
the beetles finds the food it seizes it in its mandibles and 
quickly hides with the morsel where it can devour it un- 
molested. If two or more of the beetles find the food at the 
same time, or discover one feeding, they immediately 
attempt to take the morsel away, and tug and pull the food 
about until each obtains a portion, or one manages to run 
away with the whole, of their dead comrade. Such behavior 
is only shown in the presence of food apparently, as the 
