No abstract

From 1994 to 2013, French forensic entomology laboratories investigated 1,093 cases. Larder beetles (Coleoptera: Dermestidae) were observed in 81 (7.5%) of these cases. To describe and analyze these 81 cases, eight parameters were used: city, location (indoor or outdoor), decay stage (fresh, decay, or dry), dermestid species and instar (adults and/or larvae), presence of living calliphorid larvae, presence of calliphorid pupae or adults, and presence of other necrophagous species. Eight Dermestidae species were observed: Dermestes frischii (42% of cases), Dermestes undulatus (35.8%), Dermestes peruvianus (12.3%), Dermestes lardarius (9.9%), Dermestes haemorrhoidalis (8.6%), Dermestes maculatus (7.4%), Dermestes bicolor (3.7%), and Dermestes ater (1.2%). Larder beetles primarily developed on human cadavers in outdoor locations in areas with a dry climate and were never reported in oceanic areas (which are characterized by frequent rainfall and high ambient humidity). The number of dermestid species on a single corpse never exceeded three. Typically, one species was found per corpse. Species differed between indoor and outdoor cases, with D. frischii and D. undulatus dominant in outdoor cases, while D. peruvianus dominant in indoor cases. Calliphoridae was found in 88% of the cases, while Hydrotaea and Piophilidae were observed 40% of the time. Regarding Coleoptera, Necrobia spp. (Coleoptera: Cleridae) was observed in 46% of the cases. Lastly, we observed a typical decomposition pattern, with preferential feeding areas on the face, hands, and feet (i.e., the extremities). Pupation chambers on or inside the bones were not observed.

Due to the ephemeral nature of carcasses they grow on, necrophagous blowfly larvae should minimize the time spent on the cadaver. This could be achieved by moving to high-temperature areas. On that basis, we theorized that larvae placed in a heterogeneous thermal environment would move to the higher temperature that speed up their development. This study was designed to (1) test the ability of necrophagous larvae to orientate in a heterogeneous thermal environment, and (2) compare the temperatures selected by the larvae of three common blowfly species: Lucilia sericata (Meigen), Calliphora vomitoria (L.) and Calliphora vicina (Robineau-Desvoidy). For this purpose, we designed a setup we named Thermograde. It consists of a food-supplied linear thermal gradient that allows larvae to move, feed, and grow in close-to-real conditions, and to choose to stay at a given temperature. For each species and replication, 80 young third instars were placed on the thermal gradient. The location of larvae was observed after 19 h, with fifteen replications per species. The larvae of each species formed aggregations that were always located at the same temperatures, which were highly species-specific: 33.3 AE 1.52°C for L. sericata, 29.6 AE 1.63°C for C. vomitoria, and 22.4 AE 1.55°C for C. vicina. According to the literature, these value allows a fast development of the larvae, but not to reach the maximum development rate. As control experiments clearly demonstrate that larval distribution was not due to differences in food quality, we hypothesized that the local temperature selection by larvae may result from a trade-off between development quality and duration. Indeed, temperature controls not only the development rate of the larvae, but also the quality of their growth and survival rate. Finally, results raise questions regarding the way larvae moved on the gradient and located their preferential temperature.