Abstract

SUMMARY (1) A numerical model of an ant colony of the Myrmica type has been constructed; it is determinate and based on two discrete periods each year. Food is collected round a single nest entrance, and converted inside into new ant material. This 's generated as fertilized eggs by the queen giving gynes and workers, and as unfertilized eggs by the workers, giving males. (2) Reproduction and dispersal either by swarms of workers or by the dissemination of gynes, prevent inefficiency and over-population. The production of both males and females is regulated by a similar control system that assesses the worker/queen ratio. In theory these controls can be set so that not only is sexual emission maximal, but that male and female investment are approximately the same. (3) The system grows sigmoidally and then passes into a period of stable or convergent oscillations. Oscillations are caused by time lags due to life history, by the competition of sexual brood with worker brood, and by our discrete representation of the density dependencies. Damping is caused by limited egg production, and by a system of distributing food proportionally to the brood requirements. A 'contest' system of food distribution is used. (4) When the model structure is supplied with parameters drawn from observations on natural colonies it can be shown to work most efficiently at a food supply density very near that recorded in a natural grassland habitat. (5) The phenomenon of colonies yielding only males can arise because food is

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