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Psyche 
[Vol. 88 
open field ant. Monomorium minimum is a small (head width 0.47 
mm), monomorphic species. Workers are successful at retrieving 
food particles which are either extremely small (less than 0.5 mg in 
weight) or large (greater than 450 mg in weight). Most items of 
intermediate size are lost due to either exploitative or interference 
competition from other species. Detailed laboratory and field 
experiments on the organization of foraging showed that M. 
minimum recruits other workers to food sources using trail pher- 
omones. The quantity of pheromone determines the foraging re- 
sponse of the colony. As trail pheromone concentration increases, 
more workers are recruited. The amount of trail pheromone 
deposited is dependent upon resource quality (in this case, measured 
by the investigators as weight). Large food items induce trail laying 
by many workers and therefore result in strong recruitment. If there 
is interference from another species while prey is being dissected, 
workers display a specific posture (gaster flagging) while extruding 
the sting and discharging a droplet of poison gland secretion. This 
secretion has a repellent effect on intruding ants and causes them to 
recoil and vigorously groom. The effectiveness of this defensive 
behavior is dependent on the number of workers recruited. There- 
fore, large prey, which elicit strong trail pheromone deposition, 
induce strong recruitment responses and this results in a worker 
force which can successfully defend the item during retrieval. The 
result of this feedback between prey size, pheromone concentration 
and colony response is a diet composed of small individually 
retrieved items and large items recovered by recruitment and 
successful defense. 
Perhaps the best evidence for the importance of behavioral 
parameters in species interactions is the phenomenon of alarm 
specification. Certain ant species which interact strongly with other 
species may respond specifically to the presence of the competitor. 
The best studied case is that of Pheidole dentata and Solenopsis 
geminata (Wilson 1975). Pheidole dentata colonies respond to the 
presence of Solenopsis by a strong recruitment of major workers. 
Major workers proceed to attack and kill all Solenopsis encountered 
and to search thoroughly the area near where the Solenopsis 
workers were found. They do not respond to the odors or presence 
of other species with major worker recruitment. A similar pattern of 
response is indicated in the interactions between Oecophylla longi- 
