Nocturnal oviposition behavior of blowflies (Diptera: Calliphoridae) in the southern hemisphere (South Africa and Australia) and its forensic implications.

Published research has offered contradictory evidence of the occurrence of nocturnal oviposition by carrion-breeding blowflies, a behavior that can affect the interpretation of forensic estimates of a minimum post mortem interval (minPMI) by up to 12 hours, depending on latitude and season. The majority of published studies are from the northern hemisphere. Field experiments were conducted in South Africa and Australia that extend observations to species of the southern hemisphere. Various vertebrate carrion was exposed at night in summer under different lunar phases and/or artificial lighting, and in woodland and pasture areas. Three laboratory experiments were also conducted. No nocturnal oviposition occurred outdoors in Berry, Australia, but Lucilia cuprina, Lucilia sericata and Chrysomya megacephala laid eggs outdoors at night in Grahamstown and Durban, South Africa. In laboratory experiments L. sericata, L. cuprina, Chrysomya chloropyga and Chrysomya putoria laid eggs and Calliphora augur deposited larvae under nocturnal conditions. Chrysomya albiceps and C. chloropyga laid eggs in darkness with increasing likelihood as ambient temperature increased. This study shows that nocturnal ovi/larviposition by carrion-breeding blowflies is possible in both South Africa and Australia. The forensic issue is therefore not whether nocturnal oviposition occurs, but rather whether the conditions of a particular case are more or less conducive to it. Circadian rhythms and physiological thresholds (particularly temperature and humidity) appear to act individually and in conjunction to stimulate or inhibit nocturnal laying. The significance of carcass size, freezing and handling of carcasses and comprehensive quantification for experimental design is discussed, and recommendations are made for future laboratory and case scene experiments

Seasonal Blowfly Distribution and Abundance in Fragmented Landscapes. Is It Useful in Forensic Inference about Where a Corpse Has Been Decaying?

<div><p>Blowflies are insects of forensic interest as they may indicate characteristics of the environment where a body has been laying prior to the discovery. In order to estimate changes in community related to landscape and to assess if blowfly species can be used as indicators of the landscape where a corpse has been decaying, we studied the blowfly community and how it is affected by landscape in a 7,000 km² region during a whole year. Using baited traps deployed monthly we collected 28,507 individuals of 10 calliphorid species, 7 of them well represented and distributed in the study area. Multiple Analysis of Variance found changes in abundance between seasons in the 7 analyzed species, and changes related to land use in 4 of them (<i>Calliphora vomitoria</i>, <i>Lucilia ampullacea</i>, <i>L</i>. <i>caesar</i> and <i>L</i>. <i>illustris</i>). Generalised Linear Model analyses of abundance of these species compared with landscape descriptors at different scales found only a clear significant relationship between summer abundance of <i>C. vomitoria</i> and distance to urban areas and degree of urbanisation. This relationship explained more deviance when considering the landscape composition at larger geographical scales (up to 2,500 m around sampling site). For the other species, no clear relationship between land uses and abundance was found, and therefore observed changes in their abundance patterns could be the result of other variables, probably small changes in temperature. Our results suggest that blowfly community composition cannot be used to infer in what kind of landscape a corpse has decayed, at least in highly fragmented habitats, the only exception being the summer abundance of <i>C</i>. <i>vomitoria</i>.</p></div

Invertebrate Scavenging Communities

Invertebrate scavengers of terrestrial and aquatic carrion include a broad and enormously diverse grouping of various arthropods, nematodes, and molluscs. By far the most functionally important in terrestrial ecosystems are insects, especially the flies, with crustaceans performing this role in marine ecosystems, although a multi-trophic foodweb of numerous invertebrate taxa can be found at most carcasses in most environments. The occurrence of different taxa, and the dynamics of their colonization and various competitive interactions varies across terrestrial and aquatic realms, and is greatly influenced by geographic region, climate, habitat, season, and other biotic factors. This sub-chapter focuses on the invertebrate use of carrion in both terrestrial and aquatic ecosystems, and highlights the role of different groups of invertebrates, and the biotic and abiotic factors that influence their occurrence and succession at decaying carcasses