392 
Psyche 
[December 
are too excitable and discharge the mandibular gland pheromone 
too readily to permit reliable assays of the trail pheromone on 
small groups of workers separated from their colony. For this 
reason we designed the test to utilize the undisturbed laboratory 
nest arrangement. The nest terraria are so large that artificial test 
trails 50 cm in length could be laid beginning at the nest entrance. 
Furthermore such trails could be laid over the paper bridge, and 
into the arena. 
The extrusion of the sting by recruiting Pogonomyrmex workers 
suggests that the trail pheromone is produced in one of the glands 
associated with the sting apparatus. This would not be surprising 
in view of the fact that other members of the subfamily Myrmicinae 
produce trail pheromones either in Dufour’s gland [Solenopsis (Wil- 
son 1959), Pheidole (Law et al. 1965)], or in the true poison gland 
\^Atta (Moser and Blum 1963), Tetramorium (Blum and Ross 
1965 ),Monomorium (Blum 1966)]. 
To test the effectiveness of different abdominal gland secretions, 
the hindgut, the poison gland (with vesicles), and the Dufour’s 
gland were first dissected out of workers. For each replication the 
organs of a kind from three workers were washed in distilled water 
and then crushed in 0.5 ml of benzine. Aliquots of 10 fi\ of the 
benzine solution of the gland secretions were then applied with a 
syringe along a 50-cm-long artificial trail drawn away from the 
nest entrance. During the next five minutes a count was taken 
of all the ants — except those carrying sand — that left the nest 
entrance and followed the trail to the end (Fig. 7). The data 
obtained (Table 2) show clearly that the poison gland has the 
strongest recruiting power. Since the ants also followed the artificial 
poison gland trails through each twist and turn, we conclude that the 
poison gland secretion serves both as a releaser of recruitment be- 
havior and as an orientation cue. However, in a separate study 
Holldobler (1971) found that the Dufour’s gland secretion of P. 
Poison 
Gland 
Dufour’s 
Gland 
Hindgut 
N 
M 
Range 
N 
M Range 
N 
M Range 
Colony I 
6 
77.3 
39-120 
9 
11.3 
5-27 
9 
5.1 1-12 
Colony II 
8 
97.9 
38-187 
10 
8.2 
3-18 
8 
5.1 0-17 
Colony III 
7 
81.6 
32-157 
9 
15.5 
5-29 
9 
6.1 0-12 
Table 2. 
Artificial 
trails 
composed 
of benzine solutions 
of 
different 
abdominal 
gland secretions 
were drawn 
for 
distances of 50 
cm 
from the 
nest entrance. During the next 5 minutes all the ants that followed the 
trails to the end were counted. The number of replications ( N ) and the 
mean and range of the number of responding workers are given. 
