238 
Psyche 
[September 
as though it is “marking time” with its hindlegs, which are pulled 
in beneath its abdomen in a “knock-kneed” posture (plate 18). In a 
dorsal view, consequently, only the oscillating knee can be seen 
clearly, and it is often rapidly stroked forward. The movement of 
the hindlegs, in this case, is performed independently from the other 
legs and without participation in locomotion, whereas in the ants’ 
regular, wide-treaded gait a definite pattern of alternation in partici- 
pation of all legs is maintained (plates 17 and 18, figures 2, 3 and 
4 A). 
The analysis of slow-motion pictures from a lateral view proves 
that the hindfeet often dab the substrate without the whole leg being 
obviously stroked (fig. 4 A frames 4 and 8, fig. 4 B frames 7 to 11). 
The whole distal part of the tarsus up to the metatarsus joint is 
occasionally bent down to the substrate, while the heel moves up and 
down, and the claw is sometimes raised (fig. 4 A B). In addition 
a slight dragging of the hindfoot was occasionally observed (fig. 4 A 
frame 2, fig. 4 B frame 12). The trail-laying behavior of a forager 
on her way back toward the nest is not always clear and definite. 
A continuous change from the most intensive form of shuffling to an 
almost regular walking step can be observed. Fig. 4 C shows an 
average trail-setting. Also here an autonomous foot-dabbing against 
the substrate occurs, but the feet are kept farther apart. 
In order to investigate the efficiency of a single trail-layer, an ant 
from a starved colony was allowed to find food at the end of the 
sideturn bridge. After feeding such an explorer performs a very 
strong trail-laying on her return. Trail-laying often becomes weaker 
toward the end of the long uniform part of the bridge but increases 
again when passing the obstacle of the connection from the new 
bridge to the old one. From the point onto the old trail a very brief 
but strong episode of trail-laying is typical, usually being maintained 
for only a few centimeters on the old runway. Then trail-laying 
decreases; the recruiter runs back and forth on the old trail exciting 
other nestmates, and finally she returns to the food or at least close 
to it. Trail-setting is performed even on the way toward the food, 
but usually more vigorously on the return trip. If the bridge is 
connected only for the passages of the one recruiter ant but not for 
other newcomers, this back-and-forth game can be repeated as many 
times as the observer wishes. 
It is obvious that, in most cases, the trail from one single run is not 
efficient enough to lead newcomers reliably to the goal, except on very 
short feeding bridges. The explorer ant itself, however, is usually 
able to follow its own first trail, taking cues where trail-laying was 
