Effects of bait age, larval chemical cues and nutrient depletion on colonization by forensically important Calliphorid and Sarcophagid flies.

Species colonization patterns on corpses and the frequency of carrion fly oviposition and larviposition are affected by decomposition stage and previous maggot colonization. This study investigated these effects on meat bait colonization by Victorian Diptera of forensic importance. Bait treatments were: 'aged' (aged for 4 days at 22 °C, allowing some decomposition); 'nutrient-depleted' [aged for 4 days at 22 °C with feeding Calliphora vicina (Robineau-Desvoidy) (Diptera: Calliphoridae) larvae]; 'extract' (fresh bait mixed with liquid formed by feeding C. vicina larvae), and 'fresh' (untreated control bait). Statistical analysis (α = 0.05) revealed that colonization frequency differed significantly among treatments (Welch's F(3,18.83) = 4.66, P < 0.05). Post hoc tests showed that fresh and extract baits were colonized extensively throughout the experiment with no significant difference, whereas the colonization of nutrient-depleted baits was significantly lower. This suggests that larval digestive enzymes, larval excreta and cuticular hydrocarbons have less effect on colonizing Diptera than the nutritional content of meat. The colonization of aged baits did not differ significantly from that of fresh, extract or nutrient-depleted baits. A further experiment testing 'very aged' (aged for 8 days at 28 °C), 'larvae-added' (fresh bait with C. vicina larvae added before placement) and 'fresh' (untreated control) baits revealed that very aged baits were colonized significantly less frequently than either fresh or larvae-added baits (Welch's F(2, 6.17) = 17.40, P < 0.05).

Fly pupae and puparia as potential contaminants of forensic entomology samples from sites of body discovery.

Fly pupae and puparia may contaminate forensic entomology samples at death scenes if they have originated not from human remains but from animal carcasses or other decomposing organic material. These contaminants may erroneously lengthen post-mortem interval estimates if no pupae or puparia are genuinely associated with the body. Three forensic entomology case studies are presented, in which contamination either occurred or was suspected. In the first case, blow fly puparia collected near the body were detected as contaminants because the species was inactive both when the body was found and when the deceased was last sighted reliably. The second case illustrates that contamination may be suspected at particularly squalid death scenes because of the likely presence of carcasses or organic material. The third case involves the presence at the body discovery site of numerous potentially contaminating animal carcasses. Soil samples were taken along transects to show that pupae and puparia were clustered around their probable sources.

Social isolation and delayed discovery of bodies in houses: the value of forensic pathology, anthropology, odontology and entomology in the medico-legal investigation.

The bodies of socially isolated people may remain undiscovered in their own houses for prolonged periods. Occasionally the body is in situ for sufficient time to become skeletonised, or partially so. Medico-legal investigation of these cases is complicated by degradation and contamination of evidence. Thus, a multidisciplinary forensic investigation is recommended. The potential contributions of forensic pathology, anthropology, odontology and entomology are outlined here with reference to two cases that occurred in Victoria, Australia, in 2003. Forensic pathologists are often unable to determine the cause of death in skeletonised bodies, however, they may find evidence to support either a natural or unnatural mode of death, and they may describe skeletal pathology or trauma, and identify skeletal features to support radiological identification of the deceased. Anthropologists can provide supplementary evidence of skeletal trauma. Additionally, they can assess age, sex, stature and racial affiliation from skeletal remains. Odontologists can identify individuals through comparison with ante-mortem dental records; however, potential difficulties exist in identifying the treating dentist of a socially isolated person. Odontologists may also examine the teeth and oro-facial skeleton for trauma. Entomologists may estimate minimum death time and/or season of death. Entomological examination of insect remains may also confirm that a body has lain in situ for a considerable period.

Potential contamination of forensic entomology samples collected in the mortuary: a case report.

Carrion insects originating from infested bodies may establish small mortuary populations. Two Victorian Institute of Forensic Medicine cases are presented to illustrate how these insects can potentially contaminate forensic entomology samples collected in the mortuary. The first case proves that bodies can be colonised in the mortuary: when a decomposed body in freezer storage was thawed for a procedure in the main mortuary, it was colonised within five minutes of exposure by the beetle Necrobia rufipes De Geer (Cleridae, Coleoptera). The second case illustrates that immobile juvenile insects can be transferred between bodies, and describes the transfer of an Eristalis sp. (Syrphidae, Diptera) pupa from a decomposed to a fresh body. While the contamination risk is slight, it can be further minimised by checking mortuary-collected samples against those taken from the body discovery site, by mortuary pest control, and by checking previous mortuary admittance records for possible contamination sources.

Rainfall and temperature effects on the decomposition rate of exposed neonatal remains.

There are scarce data describing seasonal effects on decomposition, and on the decomposition of neonatal remains. Piglet carcasses were exposed in a forest at Coranderrk Bushland (Victoria, Australia) each season for two years. The effects of season, year, temperature, and rainfall on mass loss rate and decay stage durations were investigated. There was a significant season and year interaction in weeks taken until the end of putrefaction: this was longest in winter, followed by autumn, spring and summer. Higher temperatures and rainfall increased both mass loss rates, and decomposition stage progression rates.

Effects of decomposition on carcass attendance in a guild of carrion-breeding flies.

Many forensically important calliphorids, sarcophagids and muscids (Diptera) oviposit or larviposit on corpses only during the early stages of decomposition, yet individuals may attend bodies throughout decay. A field study was conducted to investigate how patterns of carcass use and attendance by some fly species are affected by decomposition. Five fly traps were placed in the forest and baited with whole, fresh piglet carcasses. Piglets decomposed in traps throughout the experiment, and all were skeletonized within 6 days. Flies were trapped at both early and late decomposition stages, and the species and population structures of trap catches were compared. More flies attended carcasses early rather than late in decay. For all species, flies attending early were mainly gravid females, but few gravid females attended late in decay. No females ovi- or larviposited late in decay, whereas females of all fly species deposited offspring early in decay. The number of males trapped of each species correlated positively with the number of females with eggs at early development stages. Observations were made of fly predation by European wasps Vespula germanica Fabricius (Hymenoptera, Vespidae) and jumper ants Myrmecia pilosula Smith (Hymenoptera, Formicidae) throughout the experiment. There was a higher risk for smaller fly species of being killed following predator attack. Ants and wasps attacked smaller fly species, whereas only wasps attacked larger fly species.

Yearly activity patterns in southern Victoria (Australia) of seasonally active carrion insects.

Some seasonally active carrion invertebrates leave remnants of their presence that remain long after the completion of flesh decay. Remnants may include fly puparia (pupal cases) or insect exoskeletal elements. The presence of these remnants among old, decomposed remains can therefore indicate possible months in which death occurred. A large-scale study of the patterns of neonatal piglet decomposition and carrion insect succession in a forest was carried out in 1999 and 2000. Five fresh piglet carcasses were exposed once per season in both years and visited frequently throughout decay. Ten seasonally active taxa, likely to leave durable remnants of their presence were selected, and profiles were constructed of their activity times over the 2-year study.

Seasonal reproduction and host infestation rates for nycteribiids of the large bentwing bat.

Large numbers of the nycteribiid species Nycteribia parilis vicaria Maa, Penicillidia (Penicillidia) oceanica Bigot and Penicillidia (Penicillidia) Maa (Diptera: Nycteribiidae) were collected from the bat Miniopterus schreibersii Kuhl (Chiroptera: Vespertilionidae) during a study on this bat's population genetics conducted largely in southern Australia. Bats were trapped in all seasons and at a number of locations throughout the ranges of the nycteribiids. Nycteribia parilis vicaria was the most common species captured. Gravid females of the three species were trapped in spring and summer and gravid female P. (P.) oceanica and N. parilis vicaria were trapped in autumn. Newly emerged adults of P. (P.) oceanica and N. parilis vicaria were captured in spring and autumn. Nycteribiid loads for individual bats were low, and there was no direct evidence of a detrimental effect on bats.