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this temporal behavior sequence may have been slightly accelerated 
by the absence of food as seen in Bombus sylvarum and other 
Bombus species (Free 1955). Acceleration of the development of 
behavior of younger workers in the absence of older workers has 
also been reported for the ant species Manica rubida (Ehrhardt 
1931), Formica sanguinea (Dobrzanska 1959), Formica po/yctena 
(Chauvin 1969), and Tapinoma erraticum (Lenoir 1977). These 
researchers found that groups of young workers of the same age 
quickly organize themselves into nurses and foragers. Lenoir (1979) 
found that this behavior was sometimes reversible and after a few 
days, young workers ceased foraging and became nurses again. In 
fire ants, however, nurses did not appear to be as flexible and did 
not resume active brood tending after foraging. 
Reserves continued to tend brood when isolated as a group but 
also showed a limited tendency to forage. No delay in switching to 
foraging was evident. While reserves can be recruited by foragers for 
food collection (Sorensen et al. 1981), they normally do not leave 
the nest to forage on their own initiative (Mirenda and Vinson 
1981). Similar differeneces in the capabilities of young and middle- 
aged workers to shift to the roles of the oldest workers are seen in 
Pheido/e dentata (Oster and Wilson 1978). 
Isolated groups of foragers did feed and tend larvae in addition to 
foraging but remained primarily on the nest periphery when inactive 
rather than in the brood chamber where nurses or reserves were 
commonly found. Role flexibility in foragers with respect to brood 
tending has been seen in both Mvrmica rubra (Ehrhardt 1931) and 
M. ruginodis (Weir 1958a, b). The immediate switch that we saw for 
both foragers and reserves to tending larvae when isolated with 
them argues against exocrine gland control of behavior as seen in 
M. rubra (Cammaerts-Tricot 1974) or B. hvphorum and B. terrestris 
(Roseler 1967). A delay in response would be expected if dormant 
exocrine glands had to be reactivated (Oster and Wilson 1978). 
Location in the nest may have been more important in determining 
probability of worker response. Seeley (1982) found that tasks 
performed by honeybees are strongly influenced by nest archi- 
tecture. In the present study, proximity to larvae alone appeared to 
induce brood tending behavior by workers. The majority of foragers 
returned to foraging when nurses and reserves were added to their 
colonies. 
