Filip Turza and Krzysztof Miler described how body size affects ants' behaviour in a new paper published recently in Scientific Reports. In sand-dwelling Formica cinerea ants, workers vary considerably in size, as illustrated in the figure below.
Graph: Filip Turza. When workers (specifically foragers) from F. cinerea colonies are randomly sampled and measured, most of them turn out to be characterized by an intermediate body size. Some individuals, however, are visibly small and large.
The authors tested how differently-sized workers (small and large) behave when their nestmate is entrapped and requires help. They demonstrated that small individuals are more persistent when they rescue individuals in need.
Although in monomorphic ants (such as F. cinerea) body size is judged irrelevant, there are several other examples of body size effects in these ants. For example, small workers of Temnothorax longispinosus are more social than large ones, while large Myrmica kotokui workers are lazier than small ones. For more details, references, and the full paper see here (open access).