Exact detail estimation of post mortem interval (PMI) in the investigation of distrustful death, the forensic measurer blowflies are essential for accuracy in estimation of PMI. The family Calliphoridae species of Calliphora vicina and Lucilia cuprina. Were reared in laboratory condition for studying their time duration of different stages of life cycle under the fluctuating temperature in summer seasons. Calliphora vicina took 202 hours 45 minutes, where as the Lucilia cuprina took 226 hours 53 minutes, during summer season respectively. This study shows that forensic investigators will have to take each of these variables into consideration from the development of insects in order diptera to give clear or exact estimation of postmortem interval.