Migrations as a dynamic factor of number dynamics in mass species of leaf-eating and needle-eating insects

The regulating role of migration in the dynamics of Porthetria dispar L, an d Lymantria monacha L. numbers at different stages of the gradation cycle i s shown based on field observations and experiments. Chances in the rate of migration in these species under different ecological conditions were foun d. The thresholds of the insect population density promoting the migration activity anti Lability of spatial structure of taxa were revealed.