246 
Psyche 
[September 
QUALITATIVE AND QUANTITATIVE ASPECTS 
The odor trail in C. ashmeadi has been considered as an “explora- 
tory” trail rather than a “recruitment” trail, following the definition 
of Wilson (1963). This means that the trail directs ants from one 
place to the other without any exciting component of recruitment 
(The recruitment behavior in C. ashmeadi will be reported in a 
separate paper). The relatively long lasting time of a trail makes 
it also serve as a persistent “trunk route” (Wilson 1963). Field 
and laboratory experiments confirm that well established natural 
trails on paper last approximately 24-48 hours at 28°C with 
constantly decreasing efficiency. However, artificial trails pre- 
pared from petroleum ether extracts and exhibiting the initial effi- 
ciency of about a natural trail (rival bioassay), are shorter lasting 
than the natural ones, and their efficiency depends on the substrate 
material. They remain active longer on aluminum foil than on paper, 
in accordance with the lower threshold concentration needed to 
activate trail following on foil. For that reason aluminum foil is 
found to be the most suitable substrate for bioassay. The range of 
fading times for trails with the approximate efficiency of natural 
ones is listed below: 
Natural trail on paper, wood or aluminum foil: 24-48 hours 
Artificial trail from petroleum ether on aluminum foil: 8-10 hours 
Artificial trail from petroleum ether on paper: 2-3 hours 
Microscopic examination of artificial and natural trails provides evi- 
dence that the droplets of trail substance are smaller and more finely 
dispersed in artificial trails than in natural trails. This fact explains 
the shorter lasting effect of artificial trails. 
Pure tiny spots (20 /r in diameter) of trail liquid from the spindle 
smeared on a microslide glass took > 10 days to evaporate at 30°C 
(octadecane droplets of the same size evaporate in 5 minutes). Thus 
the pheromone appears 'to be a relatively nonvolatile substance. It 
stains blue with lipoid indicator “Sudan black” (Romeis 1948). A 
chemical analysis of the substance, also collected from natural trails, 
is being undertaken. 
A few quantitative experiments give us an approximate idea of the 
trail concentration. How much trail liquid does a leg contain? By 
optical measurement of the released droplets we obtained (from six 
legs) an average volume of 0.ii2?^l per leg. (0.137, 0.0824, 0.114, 
0.0897, O.120 and 0.12777I). From three independent experiments 
the amount of trail substance needed for a trail of natural efficiency 
(in rival trail bioassay) is calculated: 
