The Influence of Photoperiod on Development Rates of Three Species of Forensically Important Blow Flies

Environmental factors, such as temperature and photoperiod can play important roles in insect development. Numerous studies have researched insects and their responses to photoperiod, but there has been little research to show if the duration of light alters development rates in blow flies. A review of previous literature revealed differences in the light regime (L:D) reported for the study. This study examined the effects of photoperiod on development rates of Phormia regina Meigen, Cochliomyia macellaria F., and Calliphora vicina Robineau-Desvoidy using four light regimes of 0, 12, 16, and 24 h of light measured at both 20 degrees C and 26 degrees C. Environmental growth chambers were used to conduct the experiments with larvae reared on ground beef or beef liver inside 3.55-liter rearing containers. Using an analysis of variance, the results showed significant differences in development rates, from egg to adult emergence (d) among several treatments for each species at each temperature. There was a temperature by light interaction, and the data showed that the effects of light are magnified at lower temperatures. Development rates of all three species in the larval stage (egg to pupa) were the fastest when reared under cyclic light. Therefore, development rates determined from studies of forensically important species that used full light 24: 0 (L: D) h may be too slow, i.e., the post mortem interval is inaccurate. The significance of this research will allow more accurate post mortem interval determinations in medico-legal criminal investigations by pinpointing the photoperiod where development rates occur the fastest.