Folk wisdom among termite researchers holds that the average body size (mass) of workers in a subterranean termite colony (Rhinotermitidae) is associated with the age and/or vigor of the colony. In particular, extremely large individuals are frequently thought to indicate a very old, or senescent, termite colony. However, there are very little data to support this assumption. It is also difficult to understand why subterranean termite colonies of advanced age, with a continuing food supply and supplementary reproductives presumably active in egg production, should be prone to senescence. We present data from 16 years of observations on a Coptotermes formosanus Shiraki field colony demonstrating a negative proportional relationship between average individual worker mass and estimated size of the colony foraging population. These results do not explain the phenomenon of senescence, but do suggest that decline in colony population size may be predicted from a measured increase in the average individual mass of workers sampled over a given period of time.

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