1981] 
Holldobler, Moglich, & Maschwitz — Pella 
371 
know from observations by Wasmann, made more than 60 years 
ago, that these beetles are both fed and reared by their host ants. 
Both chemical and mechanical interspecific communication is in- 
volved in these unusual relationships. These aleocharines have 
broken the communication code of their host ants and are thereby 
able to live as parasites within the social system of the ant colony 
(Holldobler 1967, 1970, 1971, 1972). 
Species of the genus Pella are less advanced in their myrmeco- 
philic relationships. Rather than occupy the brood chambers of the 
ant nest, they live as scavengers and predators in the peripheral 
zones around the nest, at the garbage dumps, and on the trunk 
routes. Some of the behavioral features of Pella , however, seem to 
be very similar to those of Atemeles and Lomechusa. In fact, these 
behavioral patterns might be preadaptations for the evolution of a 
highly advanced myrmecophilic relationship in the aleocharine 
beetles. In particular, the appeasement behavior appears to be an 
important prerequisite for living closely with ants. This “gentle” 
defense technique does not cause excitement in the ants, as a 
repellent defense would do. 
Indeed, our observations indicate that Pella only rarely employ 
their strongly smelling tergal gland secretions when they are near the 
host ant colony. This defense system might be used more during the 
migration phase, when the beetles can be attacked by individual 
foraging ants. Similar results were previously obtained with Ate- 
meles (Holldobler 1970) and Lomechusa (Holldobler unpublished). 
In the presence of their host ants these species use the appeasement 
defense almost exclusively. 
The appeasement behavior also plays an important role during 
the adoption of Atemeles by their host ants. When encountering a 
worker of the host species near the ant’s nest, the beetle first offers 
the appeasement gland complex (at the abdominal tip) to the ant. 
This apparently suppresses aggressive behavior in the ant; only then 
does the beetle lower its abdomen to permit the ant access to the 
adoption glands, which are located in the paratergites. The glandu- 
lar openings are surrounded by bristles. These are grasped and used 
by the ant to carry the beetle into the brood chamber. While being 
carried, Atemeles adopts the same posture as that used by Pella 
during the “death feigning” behavior. As we have noted, the initially 
aggressive ants respond by either ignoring the beetles or else picking 
