(1) The question posed is whether the detection of density dependence is obscured by spatial and stochastic heterogeneity. (2) A mathematical model of a univoltine insect herbivore population incorporating non-random dispersal of adults and larval density dependence is constructed to examine the issue. (3) For a given mean size of the equilibrium population spatial heterogeneity enhances the detection of density dependence. (4) For a given mean size of the equilibrium population stochastic heterogeneity is neutral in its effect. (5) The detailed analysis of within-generation instar mortality does not always suffice in detecting density dependence.