How population density scales with habitat area is an important consideration for spatial population dynamics and community patterns. I examined the relationship between local population density and habitat area for an herbivorous beetle Tetraopes tetraophthalmus (Forster) inhabiting patches of its host plant Asclepias syriaca L. Field observations over 4 y (1992, 1995–97) at the same site revealed that the relationship was variable during the adult fight season. Highest densities occurred on large patches early in the season, but as the season progressed, densities tended to equilibrate among patches of various sizes. Among years the relationship also showed considerable variability, but similar within generation patterns. Considering entire generations, increasing, decreasing and constant density with patch size were observed over the four years of observation. The results of this study indicate that there is considerable within and between generation variability in the density-area relationship. How population density varies with habitat area affects conservation reserve design and underlies spatial population and community theory. Variability in density-area relationships will introduce greater uncertainty for predictions of metapopulation persistence as well as estimates of community structure. Given the degree of variability seen in this system, any single estimate of a density-area relationship would be misleading. Multiple estimates, taken both within and between generations, should be performed before applying density-area relationships in studies of spatial population dynamics, community patterns and reserve design.