Regulation of worker reproduction in the polydomous ant Aphaenogaster (Novomessor) cockerelli

A defining characteristic of eusociality across taxa is reproductive division of labor. In ants, workers rear the queen’s offspring rather than producing their own. However, if a colony becomes queenless, workers may begin producing male offspring. Aphaenogaster (Novomessor) cockerelli are a particularly interesting species of ants for studying reproductive regulation because of additional challenges imposed by polydomy. Each monogynous colony is spread among 1-5 disconnected subnests, and so many nest workers may often be physically isolated from the queen. Nest workers have active ovaries that are used to produce trophic eggs as a nutrient source, and they produce male offspring in queenless laboratory groups. However, these workers do not produce male offspring in natural subnests separated from the queen. Although A. cockerelli police reproductive workers, they are unable to cull worker-laid eggs because they are chemically indistinguishable from queen-laid eggs. In this experiment, we investigate the mechanism used to regulate worker fertility in subnests separated from the queen. Each of three groups of 50 workers were isolated from 11 queenright colonies and either given 30 eggs, 30 larvae, or no brood. They were monitored weekly to maintain brood condition and to monitor for the production of eggs. Our findings suggest that larvae delay worker fertility, but eggs have no effect. Larval inhibition is only known to occur in two other ant species, but larvae are a likely mechanism for regulating worker reproduction in A. cockerellli because they are easily transported between subnests. Additional investigation into the mechanism used by the larvae to delay worker fertilty is ongoing.