Six basic phase portraits differing in character and in the number of
their equilibrium behaviour regimes were suggested in the classificati
on of forest insect population dynamics. The portraits graphically ill
ustrate six types of dynamic behavior of numbers of the system ''phyto
phage-entomophage'': two types of stable equilibrium dynamics (station
ary and oscillatory) and four types corresponding to outbreaks of mass
reproduction-fixed, permanent, reversive and true outbreaks, respecti
vely. In this paper we consider the single parameter model, with its p
arametric domains realizing a wide spectrum of phase dynamics, both ba
sic and transitional. The changes in the phase portraits are accompani
ed by the bifurcations in the model. The results of these analyses are
in agreement with the ''stability principle of mobile ecological syst
ems'' and may supply its parameter substantiation at the model level.
(C) 1997 Academic Press Limited.