Polymorphism and polyethism in the formicinae ant Cataglyphis niger (Hymenoptera)

Worker polymorphism and its relation to colony size and polyethism was studied in the formicine ant, Cataglyphis niger. This species exhibited a slight dimorphism between the female castes and amonophasic allometry along a wide continuum of size among the workers. Worker polymorphism, however, was established progressively throughout colony development. Following the general rule in ants, the mean body size of the workers increased with colony size, and the range of worker size expanded. In the same way, the setting of individual growth parameters changed so that the allometric growth characterized by an enlargement of the head proportionally to thorax width only occurred in mature nests. In such a situation, the large workers contributed a major part of the nest guarding and foraging activities, whereas the small ones mostly performed nursing behaviors. Results were discussed with reference to previous works on other Cataglyphis species and to optimization caste theory.