1981] 
Holldobler, Moglich, & Maschwitz — Pella 
363 
chained fatty acids in the secretion of P. laticollis (Tab. 2). However, 
in none of the species could we find citronellal. 
The common presence of quinones in the tergal gland secretions 
of Pella and the related aleocharine species agree with the previous 
findings by Blum et al (1971), who found the tergal gland secretion 
of Lomeehusa strumosa to contain benzoquinone, methyl-benzo- 
quinone, ethyl-benzoquinone and n-tridecane, the latter substance 
accounting for more than 80% of the volatiles detected in the 
secretion. In addition Brand et al. (1973) analyzed the tergal gland 
secretion of Drusilla canaliculata, also an aleocharine beetle, finding 
quinones and hydroquinones together with alkanes, saturated and 
unsaturated aliphatic aldehydes. Pasteels (1968) demonstrated that 
D. canaliculata effectively employs the tergal gland secretion as a 
repellent-defense weapon against ants in a similar fashion as we 
described it for Pella. 
Although we could not find any resemblance of the Pella tergal 
gland secretions to the mandibular gland secretions of Lasius 
fuliginosus, it was noteworthy that the Pella secretions contained 
undecane, a hydrocarbon commonly found in the Dufour’s glands 
of formicine ants (for review see Blum and Hermann 1978) and 
considered to be an alarm pheromone in L. fuliginosus (Dumpert 
1972). However, isolated tergal gland secretions of P. laticollis 
elicited a repellent reaction rather than an alarm response in L. 
fuliginosus. Apparently the repellent effect of the quinones in the 
secretions is stronger than a possible alarming effect released by 
undecane. In fact, when the ant’s antennae were directly contam- 
inated with the beetles’ tergal gland secretions the antennae were 
hanging almost motionless and flabby and the ant appeared dis- 
oriented for several minutes. From all our laboratory tests it 
appears obvious that the tergal gland secretions of Pella functions as 
a powerful chemical defense weapon against attacks by ants. 
Appeasement behavior: 
When foraging on the ants’ “garbage dumps” or running along 
the ants’ trails, Pella frequently encounter ants. Yet we were 
impressed by the scarcity of their application of the tergal gland 
defensive system. Much more frequently the beetles employed an 
appeasing defensive strategy, and the repellent defense seemed to be 
employed only as a last resort. 
