1968] 
Lent hold — Crematog aster 
247 
No. of legs 
containing 
0.112/d 
(=0.112X10- 6 
ml) each 
For natural 
efficiency 
homogenized 
and diluted 
to : 
Competition 
with natural 
trail 1 :1, 
on substrate : 
Solution 
per cm on 
assay-trail 
Caculated trail 
substance 
per meter 
1500 
25000 g\ in 
petroluem 
ether 
aluminum foil 
3 /d/12cm 
0.168/d* 
20 
400 /d in 
petroluem 
ether 
paper 
2.4 nl/ 12cm 
0.112/d* 
27 
640 jid in 
water 
emulsion 
paper 
2.4 /d/12cm 
0.094/d* 
*The amount required for 1 meter of the less volatile natural trail is 
possibly higher because emission of the same odor strength lasts for a 
longer time. 
This result shows that the contents of one single leg yields about 
1 m of trail standing competition with a naturally established trail. 
The threshold concentration for trail following in a competition 
assay on aluminum foil against petroleum ether is even 20 times 
lower. However, such a trail fades within a few minutes. 
SUMMARY 
(1) Crematogaster ashmeadi lay scent trails with their hind 
feet. The trail pheromone is found to be stored in the hind tibiae 
in spindle-shaped expansions of the claw tendons. It is driven out 
through the hollow tendonfiber and released from the lower foot. 
The source of the pheromone appears to be glandular tissue coating 
the spindle, but this remains to be verified. 
(2) “Active” trail-laying behavior consists of intensive dabbing 
with the hind feet onto the substrate. It is used primarily during 
recruitment. 
(3) A less efficient, “passive” trail-laying occurs during regular 
(or at not obviously changed) walking. 
(4) The trail substance is a lipophilic material of very low 
volatility and high behavioral efficiency. 
ACKNOWLEDGEMENTS 
I wish to express thanks to Dr. E. O. Wilson for offering me the 
facilities of his laboratories and for his critical reading of the manu- 
script. I am also grateful to my wife, Elfie, for her collaboration 
