Testing the demographic consequences of cannibalism in Tribolium confusum

Flour beetles of the genus Tribolium are known for population dynamics characterized by periodic cycling in the abundance of egg and larval stages, along with stability of pupal and adult densities. Previous modeling efforts have suggested that these dynamics are internally driven by cannibalistic interactions among certain life stages. The current study examines empirically the role of cannibalism in generating the population dynamics. Populations of Tribolium confusum were physically manipulated by segregating certain stages in separate containers every four days, effectively creating a refuge from cannibalism. We experimentally manipulated rates of cannibalism of eggs and pupae by adults, and cannibalism of eggs by larvae. The stage-structured dynamics of 21 separate populations were observed for 284 d. Our results support the prediction that larval cannibalism of eggs was responsible for generating cycling among these stages. Egg cannibalism by adults tended to have a stabilizing role as did pupal cannibalism by adults. Adult densities were controlled primarily by pupal cannibalism, and in its absence adult population growth approached exponential. These experiments provide a direct test of the role of cannibalism in a long-term study of population dynamics.