The effect of starvation on the larval behavior of two forensically important species of blow flies (Diptera: Calliphoridae)

The postfeeding larval stage in blow flies is generally an irreversible condition when the fully grown third instar larvae stop feeding and give no response towards food. The larvae of most species then disperse away from their feeding medium and pupariate. There are several cases reported about the use of postfeeding larvae as forensic evidence. It is a matter of common observation that the postfeeding stage can be reached earlier than the expected time if food becomes unavailable. However, no information is available on whether postfeeding stage induced by scarcity of food is also irreversible. Similarly, the minimum period of development required by the larvae of different blow flies species to enable their survival as postfeeding larvae and pupariation in the absence of food is unknown. It was observed during the present studies that the larvae of two Chrysomya species must feed for at least 35h at 28°C in order to be capable of reaching the postfeeding stage and subsequent pupariation. Duration of the starvation period required to induce postfeeding behavior decreases with increasing age of larvae. In the case of Chrysomya megacephala, 35, 45, 55 and 65h old larvae attained irreversible postfeeding stage after 30, 20, 12 and 2h of starvation, respectively. Similarly, larvae of Chrysomya rufifacies that were 35, 45, 55 and 60h old attained irreversible postfeeding stage after 25, 16, 6 and 2h of starvation, respectively.