Comprehensives knowledge on a. hatching patterns and b. hatching parameters in the commercial mulberry silkworm, Bombyx mori L., are invariably essential for successful silkworm cocoon crop. Present study confirms the earlier reported hatching patterns under four photoperiodic conditions and further reports the untapped hatching parameters of bivoltine x bivoltine silkworm hybrid, CSR2 x CSR4, more popular in contemporary Indian sericulture. Disease free layings (DFLs) of CSR2 x CSR4 were introduced into four photoperiodic conditions; LD 12 : 12 (natural day), DD (continuous dark), LL (continuous light) and black-box conditions on the third day of oviposition, under constant temperature (25 ± 1ºC) and relative humidity (80 ± 5%). Data on precise number of silkworm larvae hatched-out from the experimental eggs were recorded on hourly basis from five replications. Experiments were repeated for five times. Recorded macroscopic data were converted into percentage and represented as chronograms. Results on hatching irrevocably corroborated that the hatching rhythm in CSR2 x CSR4 under LD 12 : 12 conditions occurred for 2 consecutive days, with less hatching on day 1. Hatching rhythmicity under DD/LL obviously occurred for two consecutive days, with hatching phase advancing under DD and delaying with LL. Thus, rhythmicity was circadian, diurnal, taking ‘lights-on’ as signal and free-ran with DD/LL. Hatching with black-box condition confined to a single day, less hatching duration, in direct response to lights-on phase. From recorded macroscopic data on egg hatching and time of hatching, egg hatching parameters such as hatching duration, percentage of total hatching, brushing and early/late born larvae were extracted while percentage of unfertilized eggs and dead eggs were directly counted from experimental eggs and later converted into percentage. Total hatching and brushing percentage were significantly high under black-box system while early/late born larval percentage under DD. Imposed photoperiodic conditions did not show any impact on unfertilized eggs (%) while dead eggs percentage was more with LL condition. Data were discussed on the importance of hatching patterns and hatching parameters in commercial silkworm egg hatching.
