Testing the demographic consequences of cannibalism in Tribolium confusum

Flour beetles of the genus Tribolium are known for population dynamics char acterized by periodic cycling in the abundance of egg and larval stages, al ong with stability of pupal and adult densities. Previous modeling efforts have suggested that these dynamics are internally driven by cannibalistic i nteractions among certain life stages. The current study examines empirical ly the role of cannibalism in generating the population dynamics. Populatio ns of Tribolium confusum were physically manipulated by segregating certain stages in separate containers every four days, effectively creating a refu ge from cannibalism. We experimentally manipulated rates of cannibalism of eggs and pupae by adults, and cannibalism of eggs by larvae. The stage-stru ctured dynamics of 21 separate populations were observed for 284 d. Our res ults support the prediction that larval cannibalism of eggs was responsible for generating cycling among these stages. Egg cannibalism by adults tende d to have a stabilizing role as did pupal cannibalism by adults. Adult dens ities were controlled primarily by pupal cannibalism, and in its absence ad ult population growth approached exponential. These experiments provide a d irect test of the role of cannibalism in a long-term study of population dy namics.