Comparative growth of V Instar silkworm (Bombyx mori L.) larval and silk gland under certain temperature and humidity conditions

Lakshminarayana Reddy, P., Sujatha, B., Shanthan Babu, M. A. and Sankar Naik, S.

The growth of V instar silkworm (Bombyx mori L.) larval and silk gland was studied in certain temperatures (25, 30 and 35 ºC) and relative humidity (RH; 60, 70 and 80%) under natural photoperiodic (LD 12: 12) conditions. Disease free layings (DFLs) of two pure silkworm breeds, Pure Mysore (PM, a multivoltine breed) and NB4D2 (a bivoltine breed), and their hybrid, PM x NB4D2 were introduced into the experimental condition on the 3rd day of oviposition till completion of cocooning. Exact weights of the larval and silk gland were recorded at every 4 hours intervals in a day (06.00, 10.00, 14.00, 18.00, 22.00 and 02.00 h.) all through the 5th instar. No circadian rhythmicity was observed, both fro larval and silk gland growths. Resolved to daily averages curves, they documented additive curvilinear (sine wave) pattern up to 6th day for larval and up to 7th day for silk gland growth. Amplitude of NB4D2 was high in all the case for larval and silk gland growth. Increase in rearing temperature and reduce in the humidity resulted in reduction of both larval and silk gland growth. The results are discussed based on our earlier publication, emphasizing the synergic effects of temperature and humidity on the larval and silk gland growth.

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