Development of Age Polyethism With Colony Maturity in Coptotermes formosanus (Isoptera: Rhinotermitidae).

Age polyethism in a social insect colony occurs when individuals of different ages perform different tasks. In termites (Isoptera), it has mostly been reported in higher termites, but elements of age polyethism were recently found in juvenile colonies of a lower termite, Coptotermes formosanus Shiraki (Rhinotermitidae). The objective of this study was to compare age polyethism in immature colonies (10-mo-old) of C. formosanus to the age polyethism observed in juvenile colonies (4-yr-old), to investigate if age polyethism emerges as soon as old workers are present, or if it emerges later on, as the colony grows and ages. Age polyethism may be displayed with different patterns in immature colonies of C. formosanus when compared with juvenile colonies, owing to a difference of environmental condition within the nest, i.e., demographics and colony size. Ten-month-old colonies were observed in planar arenas and termite activities were recorded using camcorders. Larval and worker instars were determined by measuring their head width and the occurrence of behaviors was compared with behavioral data previously obtained from 4-yr-old colonies. Workers were the major workforce in both the 10-mo-old and 4-yr-old colonies. Age polyethism was minimal in 10-mo-old colonies, but was more extensive and complex in 4-yr-old colonies. Therefore, age polyethism emerges in C. formosanus as the colony matures, and may recapitulate the transition from a one-piece colony type to an extended nest colony type, with changing conditions inside the nest as the colony grows.