Cannibalism of the Pupal Stage by Adult Flour Beetles: An Experiment and a Stochastic Model

This paper describes an experiment involving adult flour beetles (genetic strain cIV-a of Tribolium castaneum) cannibalizing their own pupae and proposes a new stochastic model for this form of cannibalism. The model differs from earlier stochastic models of predation in that it is based on the hypothesis of predator satiation, and it gives a considerably better fit to the experimental data than do the earlier ones. In the experiment the percentage survival of pupae increased rapidly as the pupal density increased. This corresponds to an earlier finding that in self-limiting populaations of cIV-a, large pupal populations are apt to be followed in time by sudden increases in adult numbers (i.e. outbreaks). The model shows that this would be expected for satiable adult predators. However, for insatiable predators, outbreaks would be unlikely. Apparently, cIV-a adults behave as if their appetites for pupae were satiable, but for most other Tribolium populations 'satiation' seems to be less important and outbreaks are uncommon.