The fierce competition in the global silk market encourages the development and application of new biotechnologies in sericulture, such as cloning. The term “clone” in Greek means “branch”. A clone is an offspring of a single organism propagated without fertilization. All cloned individuals are genetically identical and are copies of each other. Clones are obtained in different ways. In case of the silkworm, this is a parthenogenetic development, which is an unnatural way of reproduction for the silkworm. Thermoactivation of an unfertilized greene at t0=46 0C during 18, leads to inhibition of the reduction division of meiosis in the silkworm germ cells. As a result, the eggs remain with a diploid set of chromosomes and develop as zygotes. Since the female cells in the sex chromosomes of the silkworm are heterogametic, only female parthenogenetic clones develop from thermally activated eggs. This feature makes silkworm clones extremely attractive for creating 100% pure hybrids. As the sericulture globally is based on the production of hybrids of the first generation only, in order to use maximum heterosis, the accuracy of preparation of hybrids is becoming particularly important.