Survival of submerged blowfly species and their parasitoids: implications for postmortem submersion interval

Pupal survival of three blowfly species, Chrysomya albiceps, Chrysomya megacephala, and Chrysomya putoria (Diptera: Calliphoridae) and the parasitoid species Nasonia vitripennis (Hymenoptera: Pteromalidae) was studied after the pupae were experimentally submerged in water. Non-parasitized pupae at different developmental stages, 0, 24, 48, and 72 h, and parasitized pupae after 3, 8, 10, and 12 days of development were submerged for 6, 24, 48, or 72 h. Control groups for each pupal developmental stage (parasitized or not), which were not submerged, were also observed in order to compare the adult emergence rates. The survival of white pupae (0 h/age) decreased with time of submergence for all three blowfly species, showing the lowest rates compared with other experimental pupa groups. For the three blowfly species, non-parasitized pupae at 24 and 48 h of age showed survival rates above 60%. However, for pupae at 72 h of age, the survival rates decreased with increased underwater time, with less than 30% survival after 72 h in C. putoria and C. albiceps. The survival of parasitoids inside blowfly pupae that were submerged during their larval stage (3 days/age) decreased with the increase of submergence time. After the parasitoids reached the pre-pupal life stage, the survival was higher for all underwater periods. These observations can be useful in investigations of the decomposition of partially submerged bodies, or in cases of pupae found adhering to decaying flesh, hair, or clothes of corpses that were submerged after the larvae had developed and pupated.