Que font les mouches en hiver ? Étude des variations hebdomadaires et saisonnières des populations d'insectes nécrophages

Necrophagous insects usually colonize cadavers a few times after death. For this reason, they are used by forensic entomologists to estimate a minimum post-mortem interval (PMI). However, the necrophagous insect populations continuously vary on different time scales. These variations are especially noticeable during winter month, when only a few flies are usually observed, and can affect PMI estimation by forensic entomologists. We studied these variations in the north of France during 9 months using baited traps. Our results clearly show that necrophagous flies may colonize corpses even during the cold season. This is especially true for the blue bottle flies (Calliphora spp.), which were more frequently observed during cold season than during the hot one. On the other hand, the green bottle flies (Lucilia spp.) were significantly more present during the hot month than during the cold ones. In addition to seasonal effects, the ambient temperature - and mostly the insulation - greatly affects the number of flies trapped. Such conclusions are especially important for forensic entomology and highlight the necessity to analyze both insect samples and detailed weather data to properly estimate the time of death.