396 
Psyche 
[December 
the experiments to be described next, that the Dufour’s gland trails 
are longer lasting than the poison gland trails. 
In the arena a Dufour’s gland trail and a poison gland trail were 
drawn simultaneously, beginning at the entrance to the bridge and 
deviating at an angle of 45 °. Then after ten minutes in the first 
series and 25 minutes in the second series, a poison gland trail was 
laid from the nest entrance over the bridge to the arena entrance, 
stimulating ants to run immediately into the arena. A record was 
kept of the trail chosen by each ant as it continued on its course. 
The results, presented in Table 4, reveal that after 10-15 minutes 
the poison gland trail was still more attractive, but after 25-30 
minutes significantly more ants followed the Dufour’s gland trail. 
We conclude that the poison gland evaporates more rapidly relative 
to its threshold concentration than does the Dufour’s gland secretion. 
10-15 Minute Interval 
Poison Gland Dufour’s Gland 
25-30 Minute Interval 
Poison Gland Dufour’s Gland 
P < 0.3 
P < 
0.002 
N 
6 
6 
8 
8 
M ± sd 
39.2 ± 12.8 
12 ± 6.5 
7.4 ± 3.2 
26.5 ± 6.07 
Range 
26-58 
8-19 
3-12 
19-38 
Table 4. A poison gland trail and a Dufour’s gland trail were offered 
simultaneously in the arena. After 10 minutes {left) and after 25 minutes 
{right) the ants were induced to approach the two trails, and their choices 
were recorded during a period of 5 minutes. The number of replications 
{N) and the mean and range of numbers of responding ants are given. 
Recruitment trails in other Pogonomyrmex species * 
Subsequent field and laboratory studies have revealed that re- 
cruitment behavior of the kind just described for Pogonomyrmex 
badius also occurs in other members of the genus (P. occidentalism 
P. rugosuSm P. barbatus, P. marie op a , P. calif ornicus) . In P. mctri- 
copa and P. calif ornicus the change in the locomotory behavior of 
trail laying ants is particularly clear. In ordinary locomotion workers 
of these species hold their abdomen upwards (Fig. 8a). But when 
entering a new area (for example a new bridge in Fig. 1) they 
repeatedly touch the surface with the abdominal tip (Fig. 8b). A 
successful scouting ant on the other hand returns to the nest with 
the abdomen completely lowered and dragging the extruded sting 
over the surface (Fig. 8c). With the nest arrangement illustrated 
in Fig. 1 we were able to show that in the first case the ants ap- 
parently set orientation marks, whereas in the second case they lay 
*Note added in proof. 
