1988] 
Holldobler — Chemical communication 
145 
Figure 3. Schematical illustration of the outline of the gaster of a Meranoplus 
worker showing the large Dufour’s gland (D) and the poison gland (P) with its 
bulging filaments. 
from the nest and followed the Dufour’s gland trail. From these 
experiments one can conclude that both the poison and the Dufour’s 
gland serve in chemical trail communication. The poison gland 
secretions appear to function as relatively short lived recruitment 
signals. The Dufour’s gland secretions do not elicit a strong recruit- 
ment response, but they appear to be much longer lasting, and 
motivated ants follow a Dufour’s gland trail. This conclusion was 
further supported by the following experiments: 
Meranoplus workers were stimulated to leave the nest along a 5 
cm long trail drawn with a freshly crushed poison gland. After 5 cm 
this trail was continued with a trail drawn 60 minutes previously 
with Dufour’s gland secretions. Almost 83% (24) of the ants arriv- 
ing at the transition point continued to follow the Dufour’s gland 
trail through at least 10 cm. Additional observations in the labora- 
tory and in the field confirm that Meranoplus establish trails which 
are very long lasting so that they function as trunk routes. From my 
