Pupation patterns, viz. larval ripening, pharate pupal and pupal formation were diurnally predominant in the silkworm, Bombyx mori L. (PM × NB4D2), under different photoperiodic conditions. Under continuous light (LL), the rhythm damped-out. Upon circular statistical treatment of the data, the peaks expressed two distinct modes short day and long day resultant groups and these phenomena are distinct for pharate pupal formation. Duration between larval ripening and pharate pupal formation, as also between pharate pupal and pupal formation was influenced by different light/dark conditions. Duration between larval ripening and pupal formation was significantly (P < 0.05) less under LD 11:13 as compared to LD 12:12.