We study a stage-structured single species population model with
Allee effects. The asymptotic dynamics of the model depend on the
maximal growth rate of the population as well as on its initial
population size. We also investigate two models of host-parasitoid
interaction with stage-structure and Allee effects in the host.
The parasitoid population may drive the host population to
extinction in both models even if the initial host population is
beyond the Allee threshold.