Suitable triggers for timing the transition from worker to sexual production in annual eusocial insects

Abstract

The life cycle of many social insects living in seasonal environments is characterized by a period of (pure) investment into worker brood followed by a phase of pure allocation of resources to the production of sexuals. Researchers have invested some effort to find possible correlates (proximate triggers) of this transition but current empirical knowledge does not provide clear evidence. Utilizing an established theoretical model—modified to account for brood developmental time—we show that a strategy that switches to the production of sexuals at a particular (fixed) date may typically perform better than strategies linking the transition to the status of the colony in terms of attributes like worker or brood number, or the colony’s age. Our results provide rationale why the search for cues triggering the transition in investment has been inconclusive at best and suggests a number of experiments and observations that allow validating our arguments.