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[Vol. 88 
Discussion 
Much of the discussion generated by Schneirla’s brood-stimula- 
tion theory concerns the relative degree to which raiding and 
emigrations are influenced by interactions between brood and 
adults (internal processes), and by external environmental factors. 
Theoretical support for emphasizing brood-related processes stems 
not only from Schneirla’s own research with army ants (Schneirla, 
1957, 1958, 1971), but from studies of other social insects as well. 
For example, honeybee workers can collect protein-rich pollen or 
carbohydrate-rich nectar. Louveaux (1950) found that the amount 
of pollen collected by an incipient colony is small, but increases as 
the brood population increases. In another experiment (Louveaux, 
1958), he removed the colony queen from a mature colony and 
found that pollen collection was unaffected until many of the larvae 
had pupated. Further evidence of larval stimulation of adult 
foraging came from Fukuda, 1960 (in Free, 1967), who showed that 
foraging workers from a recently-divided colony collected very little 
pollen until the eggs laid by the new queen hatched into larvae. 
Finally, Free (1967) demonstrated that adult worker foraging was 
influenced more by direct access to the brood than by brood odor 
alone. Perhaps most significant was the additional finding that 
artificially feeding a colony with pollen resulted in a decrease in 
pollen collection and a corresponding increase in nectar collection. 
Although Schneirla was primarily concerned with the role of 
callow and larval excitation, he did recognize the role of food as an 
ecological parameter. Thus, at an early stage of his field research 
with the neotropical genus Eciton, he reported (Schneirla, 1938) 
that colonies frequently emigrate along the heaviest raiding route of 
that day. Nevertheless, it was Rettenmeyer (1963) who first sug- 
gested that the location and amount of captured food might 
influence not only the path of colony movements, but the very 
tendency to emigrate in the first place. The idea that colony 
excitation could be related to brood satiation has received empirical 
support from Free’s (1967) study of honeybees and from related 
research with the myrmicine ant genus Myrmica (Brian, 1957, 1962; 
Brian and Abbott, 1977; Brian and Hibble, 1963). It was therefore 
significant that by the time of Schneirla’s last field study, concerning 
emigration behavior in the paleotropical army ant genus Aenictus, 
he conceded that short-term variations in colony excitation may 
