Implications of High Temperature and Low Humidity on the Hatching in the Silkworm, Bombyx mori L. under LD 12:12 condition.

Abstract

The implications of temperature (25, 30 and 35oC) and relative humidity (RH; 60, 70 and 80%) on the hatching rhythmicity and hatching parameters (percentage and duration) were studied in the silkworm, Bombyx mori L.under natural photoperiod (LD 12 : 12). Disease free layings (DFLs) of two pure silkworm breeds, Pure Mysore (PM, a multivoltine breed) and NB4D2 (a bivoltine breed), and their hybrid, PM × NB4D2 were introduced into the experimental conditions on the 3rd day of oviposition till completion of hatching. The hatching rhythm was predominantly diurnal under all temperature and humidity conditions, with peaks just after ‘lights-on’ phase (6 hrs). Extreme temperature and humidity conditions did not alter the hatching rhythmicity,but prolonged the hatching durations, extending it to the next day, coupled with reduced hatching percentage in PM and PM × NB4D2. In NB4D2, on the other hand, hatching did not extend to the next day. Hatching percentage in this breed, however, reduced below the economic level under high temperature and low humidity conditions. The high temperature and low humidity together, though did not alter the rhythmicity, seems to exert synergetic effect on the hatching percentage and its duration in the silkworm, B. mori.