The implications of temperature (25,30 and 35$^{circ}C$) and relative humidity (60, 70 and 80%) on the pupation patterns were studied in the silkworm, Bombyx mori L. Larvae of two pure silkworm breeds, Pure Mysore (PM) and NB4D2 and their hybrid, PM ${ imes}4 NB4D2 were reared under experimental conditions under natural day photoperiodic (LD 12: 12) condition. The three developmental marker events viz., larval ripening, pharate pupal formation and pupal formation occurred at or around the beginning of the photo-phase. The computed of mean vector (equation omitted), based on the circular statistics, also confirmed the above. However, the length of mean vector, r and the mean vector angular variance, s varied according to temperature and humidity conditions imposed; the variations being non-significant. Extreme temperature and humidity conditions, however, resulted in reduction in pupation rate (%) for PM and PM ${ imes}4 NB4D2. On the other hand, in NB4D2 pupation percentage reduced below the economic level. The temperature and humidity together seems to exert synergic impact on the pupation rate at least in the silkworm Bombyx mori, L.