Factors governing dynamical behaviour of insect populations: A theoretical inquiry

Summary A difference‐equation model is presented which describes the growth of insect populations in relation to the underlying biological processes. The parameters involved in the model are sex ratio (W), mate‐searching efficiency (a), fecundity (F), survival rates before and after larval competition (SI and SII), degree of aggregation in larval distribution (1/k), degree of asymmetry in larval competition (ρ), habitat's carrying capacity (K), and intensity of mutual interference among adults (h). The model is capable of generating a wide variety of dynamical population behaviours according to the parameter conditions. The significance of individual parameters in determining patterns of those behaviours is explored on the basis of their effects on the three aspects of population pattern, i. e. minimum population size for survival, equilibrium population level, and intrinsic population stability in terms of the slope of reproduction curve at equilibrium. The conditions that are effective in reducing minimum population size for survival are high FSISII (reproductive capacity), high a and even sex ratio. The conditions that are effective in raising equilibrium population level are high K, high FSISII, high ρ, low 1/k and low h. The conditions that increases intrinsic population stability are high ρ, high 1/k, high h and low FSI. Implications of these theoretical results are discussed with reference to population characteristics of insects in nature.