RECRUITMENT TO FOOD IN 
THE ANT CREMA T'OGASTER ASHMEADI 
By R. H. Leuthold* 
The Biological Laboratories, Harvard University, Cambridge, Mass. 
INTRODUCTION 
The occurrence of mass-foraging of individuals in retrieving food 
is common in most social Hymenoptera. In ants crowds of foragers 
typically appear within a short time at a food source after it has been 
detected by the first scout ant. The recruitment of nestmates to the 
food is achieved by a mechanism of communication that consists of a 
chain of several releasing stimuli. Various behavioral patterns and 
glands are involved in the different subfamilies and tribes of ants 
in the attainment of this goal (Blum and Ross 1965, Cavill and 
Robertson 1965, Maschwitz 1964, Regnier and Law 1968, Wilson 
1963). The most widely studied element of the recruitment is trail- 
laying. Different, modified or even de novo evolved exocrine glands 
in various ant groups have become adapted to the production of 
specific trail pheromones. The basic “releaser stimuli” (definition: 
Wilson and Bossert 1963) of scent trails are in most cases reported 
to be “true attractants” (definition: Dethier et al i960) which 
cause the ants to follow trails in either direction. But in addition 
to this leading quality Wilson (1962) claims a second releaser 
effect of the trail pheromone in Solenopsis saevissima which evokes 
alert and increased running activity. Apart from the effect of the 
trail pheromone Wilson (1962) describes a typical behavior of 
homing trail-laying Solenopsis workers when they contact nestmates 
on their way: “They may do no more than rush against the en- 
countered worker for a fraction of a second before moving on again, 
but sometimes the reaction is stronger: they climb partly on top of 
the worker and, in some instances, shake their body lightly but vigor- 
ously, chiefly in a vertical plane.” Following Wilson’s interpretation 
this behavior functions solely “to bring the trail substance to the 
attention of the sister worker” and does not confer any information 
beyond the attractive effect of the trail substance. 
In Crematogaster ashjneadi a similar behavior, possibly with 
simultaneous release of a pheromone, appears to have evolved into 
an important constituent of the recruitment to the food. Goetsch 
(1934) mentions “alarm” behavior of recruiting workers in Crema- 
*Present address: Zoologisches Institut der Universitat Bern, Switzerland. 
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