Temporal Variation in Colony Populations of the Ant Myrmica sulcinodis: I. Changes in Queen Number, Worker Number and Spring Production

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Abstract
Colonies of the ant, Myrmica sulcinodis Nyl., were excavated in early summer 1979-85 at two heathland sites in southern England, UK. The number of workers was, on average, 120 per colony, but varied with time and between the sites; this is interpreted in terms of a regenerating heathland habitat. The number of new workers, reared in spring, varied annually: much of the variation is explained by the size of the colonies and most of the remainder by the effects of weather during the larval growth period. Spring humidity is a good descriptor of new worker production, although humidity itself is merely a combined expression of several other climatic variables. The number of queens in the colony had no effect on the number of new workers that were reared. New queens are reared by less than 25% of the colonies. The number of queens varied annually; once the effect due to variation in the size of colonies was removed, the number followed a cycle best described by a sine-wave. The wave has a periodicity of 4-5 years and an amplitude of about three queens (1-3.3 geometric averages) in a colony of average size. This may be the first demonstration of such a cycle. The mechanisms that might generate this are discussed briefly: the periodicity may repesent the average longevity of the queens.