62 
Psyche 
[March 
increasing decomposition time of the dead ants. There are at least 
2 possible explanations to this phenomena: 
1. The chemical releaser for digging behavior is produced some- 
where inside the ant’s body and, therefore, requires some time to 
diffuse to the surface of a dead worker to become active. This dif- 
fusion time is reduced if the workers are homogenized. 
2. The responsible pheromone is a product of decomposition. 
Decomposition starts slower in intact ants, because an uninjured 
integument represents a certain barrier for external factors which 
induce or accelerate the decomposition process. 
The first explanation is weakened by the fact that I did not suc- 
ceed in localizing a gland responsible for the production of a phero- 
mone. The second explanation, on the other hand, is slightly supported 
by the following finding: In Solenopsis saevissima , products of de- 
composition accumulate in the body of dead workers no sooner than 
24 hours (Wilson et al. 1958). That is about the period during 
which I could not observe any digging behavior toward trapped 
geminata-corpses (see Fig. 2). Looking therefore for volatile prod- 
ucts of decomposition that are also emitted by the living ants and 
brood, it seemed reasonable to suspect a substance such as carbon 
dioxide. 
To obtain initial information about the value of this prediction, 
a small plastic container holding 0.5 ml of 1 M NaOH was in- 
troduced into the space between top and bottom of the stopper (cf. 
Fig. 1 ) . A second stopper was prepared in the same way, but the 
container was filled only with 0.5 ml distilled water. Each stopper 
was used to seal a vial containing 150 workers. A third bottle did 
not contain ants and its container was empty. Table 2 shows that 
the presence of NaOH — a powerful absorbent for C 0 2 — actually 
influences the digging behavior negatively. It reduces the average 
digging response to almost the same low level as found in the control. 
Table 2. Effect of NaOH on the digging behavior of ants toward 
trapped nestmates. Number of repetitions: 10. 
Number of 
trapped ants 
Contents of 
inserted container 
Average 
digging 
response 
Range 
150 
0.5 ml H 2 0 dist. 
3.6 
1-6 
150 
0.5 ml 1 M NaOH 
0.5 
0-2 
O (control) 
empty 
O.I 
01 
