376 
Psyche 
[December 
In the course of nightly studies of colony emigrations and bivouac 
locations, during the summers of 1966 and 1968, as many as 15 in- 
dividuals of H. latitarsis and H. ferrugineus were found feeding on 
the booty and on the broods of N. nigrescens. The beetles were 
observed running in army ant columns or standing off to the sides 
of the columns, behind rocks or beneath clusters of leaf litter. During 
their predatory activities, beetles ran along the trails in both direc- 
tions, “plowing” through the continuous two-way ant traffic. When 
a beetle of either species contacted a worker ant bringing booty back 
to her bivouac, the ant usually dropped the booty. On some occasions, 
if the booty was a larval or pupal individual of another ant species, 
the beetle immediately ate it and continued on the trail. On other 
occasions the beetle picked up the dropped booty, left the raiding 
column, and proceeded to a nearby rock. There, the beetle quickly 
ate the larva or pupa, returned to the column, and resumed running 
along the trail. 
On two occasions, I observed individuals of >//. latitarsis “forcibly” 
taking booty from ants. In both instances a beetle encountered an 
adult worker returning to the bivouac with a larva of the ant 
Pheidole sp. protruding anteriorly from her mandibles. The beetle 
grasped the protruding portion of the larva with its mandibles, while 
the worker of N. nigrescens was still holding the larva. The beetle 
then flexed its head sharply upwards, lifting both ant worker and 
larva, and held them off the ground for almost two seconds; the ant 
then released the larva and dropped back onto the ground. On the 
first occasion, the beetle immediately ate the larva. The second time, 
the beetle scampered away from the column with the larva as soon 
as the ant had released it. 
Both species of beetles fed most intensively on nights during the 
nomadic phase when colonies of N. nigrescens emigrated with their 
larval broods. Individuals of H. latitarsis , the larger of the two 
species of beetles, were often observed eating as many as 28 larvae. 
Whenever a beetle encountered a brood cache, consisting of several 
hundred larvae clustered beneath a leaf at a trail junction, it fed 
rapidly until satiated. As the beetles consumed the ant larvae, their 
abdominal solerites separated, and their abdomens swelled until they 
protruded considerably beyond the posterior edges of their elytra 
(Fig. 1). 
Once beetles became associated with a colony of ants, they either 
fed briefly on booty or brood and then wandered off, or they remained 
near the colony throughout the night. In the latter case, when army 
