The Growth and development of insects, including the mulberry silkworm, Bombyx mori L. are directly affected invariably by external environmental factors, such as photoperiod, temperature and humidity. While sufficient published information on the impact of photoperiod on B. mori is available, critical information on temperature and humidity impacts on Bombyx silkworm is not available. The present communication describes such issues on identification of suitable temperature and humidity conditions for rearing commercial mulberry silkworm hybrids through multiple trait evaluation index method. Five temperature conditions (20, 25, 30, 35 and 40 °C) and five humidity conditions (RH; 50, 60, 70, 80 and 90%) were selected. Two popular silkworm hybrids (PM x CSR2, a multivoltine x bivoltine hybrid and CSR2 x CSR4, a bivoltine x bivoltine hybrid) were reared under the above temperature and humidity conditions, with LD 12 : 12 photoperiodic condition from egg hatching to cocoon harvest. Three rearing characteristics; hatching (%), ERR (effective rate of rearing) by number (number of cocoons harvested/104 larvae) and ERR by weight (cocoon yield in Kg./104 larvae) were considered to determine the suitability or otherwise of enrolled temperature and humidity conditions through multiple trait evaluation index. Based on the results on evaluation index (EI) two temperature (25 and 30 °C) and two humidity conditions (RH; 70 and 80%) registered higher values of EI > 50 and designated as suitable temperature and humidity conditions. Further, comparison of average EI values of three traits revealed that average EI is highest with 25 °C temperature and 80% RH conditions alone.
