Hatching pattern in the silkworm,Bombyx mori L. (PM × NB4D2) under different photoperiodic conditions was studied. Hatching was predominantly diurnal under natural solar day conditions (LD 12:12). The observed LD pattern prevailed under all the photoperiodic conditions. Hatching confined to a single day under all the short-day conditions as also LD 12:12 and DD conditions. All the long-day photoperiodic conditions, as also continuous light (LL), resulted in broadening of the hatching peaks with reduced amplitudes, with extended hatching for two days apart from long hatching durations with more hatching on the second day. The hatching rhythmicity seems to be under circadian control. Maximum hatching was observed under LD 11:13 photoperiodic combination. Shortest hatching duration was observed under LD 11:13 condition.