Analysis of changes in numbers of the lime aphid, Eucallipterus tiliae L., reveals that there is an overcompensated density dependent factor acting within years, and an inverse density dependent factor acting between years. Because of its effect on the aphid's rate of development and reproduction the variation in temperature from year to year acts as a density disturbing factor.There is no evidence from laboratory experiments to suggest that the quality of its food influences the numbers of the lime aphid. However, qualitative changes in the aphid following period of aphid abundance are shown to be important in the overcompensated density dependent response. The more prevalent insect predators influence the regulating process as they eat most of the aphids that remain after an aphid population has declined from a very high level of abundance. Their action results in a more overcompensated response than would occur in their absence.