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the ability of many insect groups to produce from one to several generations a year. Species producing one generation a year are called univoltine species; those producing two generations are bivoltine; and those producing several generations, polyvoltine. Some univoltine species are, for example, flea beetles, most of the Acridoidea, and cereal shield bugs. The codling moth and large white cabbage butterfly are univoltine in the north and polyvoltine in the south of Russia.
The ability of the Chinese silkworm to produce from one to seven or eight generations (harvests of cocoons) a year is one of the characteristics by which silkworm varieties are distinguished. The butterflies of bivoltine varieties are smaller than those of univoltine varieties, and the quality of the cocoons spun by the caterpillars is lower, but the bivoltine varieties are quick to mature and are hardy. Crossbreeding bivoltine varieties with univoltine varieties which yield higher quality silk results in new silkworm breeds distinguished by high viability, large cocoons, high silk yield, and good technological qualities of their silk.
REFERENCESMikhailov, E. N., and P. A. Kovalev. Selektsiia i plemennoe delo v shelkovodstve. Moscow, 1956.
Uchebnaia kniga shelkovoda. Moscow, 1966.
Bei-Bienko, G. Ia. Obshchaia entomologiia. Moscow, 1966.
P. A. KOVALEV