1968] 
Leuthold — Crematogaster 
235 
together with ioo gl of petroleum ether as a standard solution. All 
bioassays were executed on the main bridge of a laboratory nest 
during times that the traffic on the trail was moderate. By coating the 
times that the traffic on the trail was moderate. By coating the 
cylindrical bridge with a io cm wide strip of aluminum foil the old 
trail was interrupted. Two rival artificial trails crossing each other 
in the form of an “8” were laid over the foil and offered to the ants 
(fig. i). Both trails had ben drawn out of 2.4/ff of a standard 
extract and were offered the ants after evaporation of the solvent. 
If in such a case neither trail is active some ants show no particular 
preference to one over the other and they may well follow either 
trail just as they do on any kind of line leading in the general right 
direction. With rival trails, however, each ant must decide twice 
between two different lines to follow, once at the start of the trails 
and once again at their crossing point. If only one of the lines 
contains a trace of the real trail pheromone it is closely followed 
by almost ioo% of all trail-follower ants (a basic rate of non- 
followers of i to 12%, depending on the degree of starvation, is 
normally observed also on natural trails) . In cases in which both 
trails contained some active component, one of them was claimed to 
be dominant only when it was followed by at least 75% of all trail 
followers in three successive assays. 
To establish the morphological site of the origin of the trail 
pheromone the following methods were used : dissection of the 
hindlegs under water, microscopy of unpigmented legs of old pupae, 
and cross-sectioning of adult legs. 
The histological techniques employed are: 
1. Fixation of whole legs (with incisions in femur, tibia and meta- 
tarsus) in 3% glutaraldehyde in a phosphate buffer of pH 
7 . 3 - 74 . # 
2. Embedding into Maraglas (an Epoxy embedding media) (after 
Erlandson 1964). 
3. Staining with methylene blue for light microscopy. 
The quality of the sections was high, but the rate of loss was too 
great to obtain complete series. 
TRAIL-LAYING BEHAVIOR 
Individuals of C. ashmeadi returning from a newly discovered 
food source (see methods) shuffle their hindlegs and never touch the 
soil with their abdomen as other ants do. The method of trail-laying 
in C. ashmeadi results in a more or less deliberate setting of foot- 
prints. A very active trail-laying ant moves slowly and looks almost 
