Journal of Ecophysiology & Occupational Health

Effects of latitude and altitude related factors like photoperiod and temperature were studied on diapause induction in tropical tasar silkworm Antheraea mylitta Drury during second crop with locally available stocks. Multiple factor regression analysis was done to observe the joint contribution of abiotic and biological factors in relation to diapause percent in second crop individuals. The result showed that the resultant contribution of altitude, latitude, minimum temperature, maximum temperature, photoperiod and larval duration was recorded to be 82.60 percent in enhancing the diapause percent. Minimum temperature plays a determining role for programming this species to enter into diapause (facultative diapause). Strong correlation exists in between photoperiod, larval period, maximum and minimum temperature, diapause percent with commercial characters like cocoon weight, larval period and silk ratios. At low latitudes, photoperiodic variation during a year is low and the stock behaves as TV. Total photoperiod received during larval span is lower in stocks behaving as TV and higher in stocks behaving as BV. Lower peak of photoperiod during yearly cycle is reflective of higher temperature and multivoltinism at low latitudes. Higher altitude has similar effect to that of higher latitude, i.e., low temperature and lower number of life cycles in a year. Based on the observations, it can be said that main tropical tasar tract of India can be considered as TV zone, excluding the areas having lower temperature due to high altitude and dense forest and the dry and hot area where 1^st crop emergence is late for want of congenial atmosphere and availability of leaves.