286 
Psyche 
[Vol. 95 
spermatheca are excluded, there is not always a precise correspon- 
dence between Buschinger’s new terms and the phenotypes of adult 
females. A case in point might be a species with ergatoid queens 
where queen-worker dimorphism is most obvious with respect to 
internal differences such as reproductive organs. Buschinger’s 
nomenclature has a clear taxonomic aim: visual appearance and 
role are combined in order to identify colony members. In contrast, 
we advocate that the terms “queen” and “worker” be used consist- 
ently in a structural sense across all highly-eusocial species, so as to 
gain an evolutionary perspective of the developmental origin of 
reproductive individuals. It is only in a minority of ant species that 
there will be a need for appropriate modifiers to describe roles (or 
appearance, e.g. “ergatoid”). 
Conclusions 
“Queen”, “worker”, and “caste” are deeply embedded in the litera- 
ture on eusociality, yet they are currently ambiguous. Reproductive 
division of labor, and the occurrence of (phenotypic) castes, are two 
completely distinct phenomena associated with eusociality — the 
former can occur without the latter. A more rigorous use of these 
terms, with the emphasis on morphology rather than on function, is 
likely to produce a better insight into various evolutionary modifi- 
cations associated with eusocial organization, for example repro- 
duction by mated workers in some ponerine ants. Wheeler (1986) 
emphasized that increased complexity of social organization has 
required changes in the underlying developmental programs that 
produce the members of* a society. The evolutionary divergence of 
queen and worker morphology in some groups is thus fundamental, 
and this must be appreciated through a discriminating use of the 
terminology. 
Summary 
The term “caste” has an equivocal meaning in writings on eusocial 
Hymenoptera. It is used in a morphological sense to describe the 
different female phenotypes which result from separate patterns of 
larval development, or it is used in a functional sense to describe 
reproductive role (or the individuals who perform that role). Sim- 
ilarly, “queen” and “worker” have alternative definitions. Various 
authors use “queen” to describe the phenotype which is a result of 
morphological adaptations for more efficient reproduction. Others 
