1969] 
Hangartner — Solenopsis 
59 
stopper and blocked again by gluing a piece of an index card (Ox- 
ford, 7182 B) to it. The bottom of this stopper was perforated with 
a needle approximately 50 times, which allowed volatiles produced 
inside the vial to penetrate but at the same time prevented contact 
between the trapped ants and the cardboard. A capillary (i.d. 1 mm) 
was efficient enough to supply the trapped ants with the necessary 
oxygen, and a layer of moist cotton guaranteed the essential humidity. 
The control bottle was prepared in the same way but contained only 
moist cotton. The test- and the control-tube were presented simul- 
Figure 1. Arrangement used to measure the digging activity of Solenopsis 
geminata released by trapped nestmates. 
V Glass vial 
S Plastic-Stopper 
C Cardboard blocking a hole (6 mm) punched 
through the top of the stopper 
B Perforated bottom of the stopper 
G Glass capillary (gas exchange) 
CG Copper gauze 
M Moist cotton. 
