Hybrid larvae of B. mori, the result of interbreeding between Chinese breeds. (c37 strain) and Japanese breeds (M11-2 strain) at the third instar of development were obtained from the germplasm bank of the UEM, Parana, Brazil. The larvae were placed in polyethy lene boxes and kept in the breeding ro at atemperature of23 c and humidity of 70% (Hanada and Watanabe, 1986) They were fed fresh mulberry leaves (Morus sp.) three times a day ad libitum.