1981] 
Holldobler, Moglich, & Maschwitz — Pella 
365 
It was especially common in early spring, when most of the 
beetles were found close to the entrance of the ants’ nest, that the 
beetles showed “death feigning” behavior, when attacked by ants. 
They fell to the side, the legs and antennae folded tightly to the body 
and the abdomen curved upwards (Fig. 5A). The ants either ignored 
these motionless beetles or carried them around and finally dis- 
carded them on the “garbage dump”. But only rarely did they injure 
the beetles (Fig. 5B). 
Later in the year, when the activity of ants and beetles was much 
higher, the beetles employed a different appeasement technique. As 
mentioned before, we only very rarely saw the discharge of tergal 
gland secretions by the beetles, although every time they en- 
countered ants they flexed their abdomen and pointed with the 
abdominal tip toward the head of their adversaries. Usually the ants 
responded by antennating the tip and briefly licking it (Fig. 5C). 
This ordinarily slowed down the ants’ aggression and the beetles 
used the ants’ distraction to escape. Occasionally, when the ants 
remained very persistent, a white, viscous droplet appeared at the 
abdominal tip, whereupon the ants usually very eagerly licked it up. 
This appeasing defensive behavior was much more common during 
the interactions between Pella and Lasius fuliginosus than the 
repellent defense. For a series of simulation experiments we cut off 
the last 3 segments of the abdomen of freshly killed P. laticollis, 
sealed the cut with wax, pinned the segments on dissecting needles 
and presented these “dummies” to the ants. In a total of 60 tests 
(using 3 different dummies) the ants interrupted their run in 47 cases 
(78%) and licked the abdominal tip briefly. 
Histological investigations revealed that the abdominal tips of 
Pella are batteries of exocrine glandular structures, all of which 
together we call the appeasement gland complex. In the following 
section we give a brief description of the glands which could be 
involved in the appeasement behavior. 
The most comprehensive study of the glandular morphology of 
some termitophilous and myrmecophilous aleocharine beetles has 
been published by Pasteels (1968). From this work we learned that 
these beetles possess a surprising variety of exocrine glandular 
structures and that various species can differ considerably in their 
glandular systems. In the four species of Pella ( P . cognata, P. 
funesta, P. humeralis, P. laticollis ) we investigated, we did not find 
major differences, although P. humeralis appeared to be somewhat 
