The biology and silk production of the mulberry silkworm Bornbyx mori L. (hatchability, rate of larval mortality, larval duration, silk content ratio and silk filament size) were insignificantly affected when eggs after 8-10 days of incubation were stored under cooling at (4-7°C) for 6 days. Cooling delayed hatching date for 11-12 days. Cold storage of newly hatched larvae a. 12°C for 3 days or at 15OC for 2 days insignifi­cantly affected the above-mentioned aspects of biology and silk produc­tion. Cooling treatments delayed the date of initial rearing by 4-5 days compared to the control.