Termite (Apicotermes) Nests-Important Ethological Material

The subterranean nests of the African genus of termites, Apicotermes, present unique material for the study of the evolution of behavior. The nests are species-specific and show phylogenetic relationships much more clearly than do the morphological characteristics of the termites building them. Unusually complete phylogenetic series are found. The phylogeny of Apicotermes, although based largely upon nest characteristics, is also corroborated by taxonomic, zoogeographical, and ecological data. The evolution of nest-building behavior in Apicotermes illustrates particularly well several similarities to the evolution of structural characteristics. Circular galleries seem to have evolved independently four times within the genus. Wall perforations, the most characteristic feature of the genus, seem to have the function of permitting gas exchange across the nest wall. The circular galleries apparently serve to protect these perforations (probably from ground water). The nest of one species has lost the wall perforations through regressive evolution, while the nest of another species seems to be at an earlier stage of this regression. The ontogeny of galleries seems to recapitulate the evolutionary stages of this structure. The nest-building behavior of termites is instinctive, or innate. Behavioral characteristics evolve by the same processess as do structural characteristics.