<p>The article represents the ndings om the studies of the impacts of cold induction on the viability of caterpillars in the course of a family fa ening. Due to provocation of the latent virus of a nuclear polyhedral disease by cold exposure on caterpillars of the ‘Ya-120’ and ‘Ipakchi 2’ breed families as well as on those of lines 27 and 28, the ‘Ya-120’ and ‘Ipakchi 2’ caterpillar breeds were proved to be the most viable.</p>