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havior. A colony labor profile by age class could be an artifact of 
previous colony needs and activities, specifically for the period 
previous to the study by just less than an average worker life span. 
For instance, suppose that a colony engaged in high brood 
production several weeks previous to observations. There would 
have been both need and opportunity for much brood care, and also 
opportunity for fixation on brood tasks. Further imagine that the 
food supply then dwindled and brood production decreased. Some 
older workers are fixated on and keep performing brood care tasks, 
leaving little need for younger workers to perform this task, and 
therefore little opportunity for task fixation. At the time of 
observation, RPM for brood care would show older castes 
performing proportionately more brood care. Yet it may be 
misleading and actually incorrect to draw the conclusion that older 
castes “typically” perform brood care. RPM are epiphenomena of 
past (and current) colony labor needs, and may say less about age 
castes as such than about behavioral flexibility and colony require- 
ments. Therefore, appropriate conclusions must consider this, and 
include at least a time frame, plus consideration of colony age, size, 
and circumstance. 
3. Continuous versus discrete castes; roles 
By definition, discretization of age castes is a direct consequence 
of roles (a group of tasks) linked by high transition probabilities, 
and exclusively or principally performed by a particular age caste 
(Oster and Wilson 1978, Wilson 1976a). Our results for P. hortensis 
show a continuous mode and, therefore, no roles. This differs from 
results of other age polyethism studies. Wilson (1976a) and Seeley 
(1982) find behavioral discretization by age, and roles. Both also 
argue that spatial efficiency is its basis, with each role (suite of tasks) 
involving a set of physically proximate contingencies. If that is the 
case, differences among the species and especially between P. 
hortensis and P. dentata, could account for the results. Colony size 
in P. hortensis is a few hundred, in comparison with up to a 
thousand in P. dentata. The former nests in twigs or small nuts, the 
latter in logs often with underground galleries. Thus for P. 
hortensis, spatial efficiency may be an irrelevant consideration. 
However, other more basic considerations may also be involved. 
Mirenda and Vinson (1981) elaborate on Wilson’s (1976a) use of 
