1968] 
Leuthold — Crematogaster 
243 
leg. This bioassay, repeated positively five times, proved that this 
oil-like substance is, or at least contains the trail pheromone. 
As evidence that the spindle reservoir is part of the tendon, it can 
be shown that pulling the reservoir slightly with a pair of forceps 
moves the pretarsus. The whole tendon organ can also easily be 
pulled out from the leg together with the attached muscles and with 
an oblong mass of tissue partially coating the spindle (pi. 19 B). The 
spindle itself is rather stiff and the fibers are relatively tough. The 
distal fiber of the tendon however always tears off somewhere in the 
mesotarsus. The content of the spindle is easily stained blue with 
Sudan black (Romeis 1948) by dipping the whole organ into a 50% 
alcoholic stain solution (pi. 19 C D). This procedure shows that 
the spindle is filled only with lipophile substance. Sometimes an 
empty space, illustrated in pi. 19 C, can be seen which might be an 
artifact of stretching. On a microslide, a slight and careful pressure 
on the coverglass drives the blue liquid up to, but not beyond a place 
which corresponds approximately to the knee between femur and tibia 
(pi. 19 D). Like a folded fire hose, expanded by the pressure of the 
water, this upper part is opened by internal pressure. The lower 
extension of the spindle, however, is stiff and hollow. Tiny blue 
droplets were successfully driven out at the place of the distal end, 
of the metatarsus. However, the spindle sometimes collapsed before 
this emission occurred. Also, such droplets could be driven out by 
pressure on the tibia after opening up the tendon at the lower end 
of the metatarsus but not beyond this place (pi. 19 A). 
The natural opening to disperse the trail pheromone is believed to 
be in the pretarsus, but this location has not been conclusively 
established yet. From the partially complete histological series of 
cross sections there is no evidence for the tendon lumen to be dis- 
continuous (pi. 19 E) and no side exit has been found. As far as 
it is conclusive from the cross sections and from total micro-prepara- 
tions, it may be that the tendon lumen opens into the ventral area 
on the end of the fifth tarsomere (pretarsus). Further histological 
investigation is in progress. The analysis of the hindleg movement 
in trail-laying individuals supports the idea that the pheromone is 
spread from the pretarsus (fig. 4 A B). On the other hand, it does 
Fig. 4. (opposite page) — Slow motion sequences (64 frames per second) 
of trail-laying ants. 
A. Hindlegs from lateral view 
B. Foot movements from lateral view 
C. Moderately active trail-laying from dorsal view (short black 
lines indicate positions on the legs in contact with surface). 
