Gail S. Anderson

Initial Studies on Insect Succession on Carrion in Southwestern British Columbia

This is the first report of an ongoing study of insect succession on carrion in British Columbia. Pig (Sus scrofa L.) carcasses were used as human models to determine insect succession on carrion over time in an open, sunlit, rural area in summer in southwestern British Columbia, in order to begin a database of insect colonization of carrion in this province. Insects colonized the remains in sequence over 271 days postmortem. Some species, in particular, those in the Piophilidae and Dermestidae families, were collected earlier in the decomposition process than usually reported from other regions, probably indicating geographic variation in colonization times. Maggot activity raised internal carcass temperature, but minimum and maximum internal temperatures fluctuated more than ambient temperatures, with diel internal temperature differences of more than 35°C. Soil fauna also showed considerable changes in identity and number of species, and had not returned to pre-carcass levels 271 days postmortem.

A DNA-Based Approach to the Identification of Insect Species Used for Postmorten Interval Estimation

Insect larvae found on a corpse can be used for estimating postmortem intervals. Here, we describe a molecular method for rapid identification of these insects. Specific insect DNA fragments were amplified using the polymerase chain reaction (PCR), followed by direct DNA sequencing of the amplification products. We sequenced 2300 base pairs of mitochondrial DNA from each of three blowfly species: Phormia regina, Phaenicia sericata and Lucilia illustris. All three species are important in forensic entomology. We found 118 nucleotide differences between the L. illustris and P. sericata sequences, 186 between L. illustris and P. regina, and 192 between P. sericata and P. regina. Based on these abundant DNA sequence differences, we can unambiguously identify the immature larval stages of these insects. These DNA sequence differences were also used to predict species-specific, diagnostic restriction sites in the amplified DNA, and these predictions were verified by digestion with nine restriction enzymes. The DNA sequences reported here encode the mitochondrial COI, COII and tRNA-leucine genes.

Insect Succession on Buried Carrion in Two Biogeoclimatic Zones of British Columbia

We established a database of insect succession on buried carrion in two biogeoclimatic zones of British Columbia over a 16-month period beginning June 1995. Pig (Sus scrofa L.) carcasses were buried shortly after death in the Coastal Western Hemlock and Sub-boreal Spruce biogeoclimatic zones of British Columbia. Buried pigs exhibited a distinct pattern of succession from that which occurred on above-ground carrion. The species composition and time of colonization for particular species differed between the two zones. Therefore ideally, a database of insect succession on buried carrion should be established for each major biogeoclimatic zone. We did not observe maggot masses on any of the buried carcasses; therefore, the presence of maggot masses may indicate a delayed burial. Soil temperature was a better indicator of internal buried carcass temperature (r2 = 0.92, p < 0.0001) than was ambient air temperature (r2 = 0.60, p < 0.0001); thus soil temperature should be used to determine developmental rates of insects for determination of the postmortem interval by a forensic entomologist.

Insect succession and decomposition patterns on shaded and sunlit carrion in Saskatchewan in three different seasons

A study was conducted on decomposition and insect succession in the Prairie Ecozone of Saskatchewan in the year 2000. Eighteen domestic pig carcasses (42-79 kg) were employed as human models for applications to future homicide investigations in this region. Two major variables were considered including the effect of season and habitat (sun versus shade). Research was conducted over 25 weeks, spanning three seasons: spring, summer and fall. Ambient temperature, internal carcass temperature, faunistic succession over time, and the rate of decay were all compared for each experimental variable. Results indicated that habitat was only a factor in the decompositional rate of carrion in the spring season. The ambient temperature was the chief factor determining the seasonal variations in decay rate. Maximum internal carcass temperatures always coincided with the presence of 3rd instar larvae. Patterns of insect succession occurred in a predictable sequence that varied across different habitats and seasons and was unique compared to previously published studies. Carcasses placed in spring and fall attracted a more diverse assemblage of insects than summer-placed carrion. Sun-exposed carrion also had greater variation in fauna than shaded carrion in spring and fall. Members of Silphidae were the first coleopteran colonizers in all habitats and seasons. This paper also marks the first record for Cochliomyia macellaria (Fabricius) in Saskatchewan.

Comparison of Decomposition Rates and Faunal Colonization of Carrion in Indoor and Outdoor Environments

Abstract:  Decomposition and insect colonization of pig (Sus scrofa L.) carcasses were observed over a 42‐day period inside and outside a house in a suburban region of Edmonton, Alberta. Three freshly killed pig carcasses were placed outdoors on grass and three carcasses were placed in separate rooms inside a house in a suburban residential area. The carcasses were examined and sampled regularly. Outside carcasses were colonized rapidly by Calliphora vicina (R‐D), Lucilia sericata (Meigen), Lucilia illustris (Meigen), Eucalliphora latifrons (Hough), Cynomya cadaverina (R‐D), Phormia regina (Meigen), and Protophormia terraenovae (R‐D). There was a delay of 5 days before inside carcasses were first colonized but all species except E. latifrons and L. illustris readily colonized at this time. Many more insects colonized the outside carcasses, and these were rapidly skeletonized. Inside, much fewer insects were present and decomposition was slowed and colonization extended. Dispersal patterns of postfeeding larvae inside the house on hard substrate were greatly expanded compared with those from carcasses on grass.

The use of Insects in Death Investigations: An Analysis of Cases in British Columbia over a Five Year Period

ABSTRACTForty-two forensic entomology cases, from human death investigations in British Columbia, (B.C.) were analyzed. The insects collected from the remains were identified based on species, developmental stage, and age of remains to begin a database for B.C. Cases also were summarized by habitat and geographical region, toxicology, manner of death and season of discovery. Most of the cases were from the Vancouver region, and were found in primarily rural situations, although many were found inside dwellings or enclosures. Drugs and/or alcohol were detected in 80% of cases tested. Most of the 42 cases were the result of homicide, and although detected year-round, occurred primarily between June and October.

Time of Submergence Using Aquatic Invertebrate Succession and Decompositional Changes

Pig carcasses were placed in pond and stream habitats in the Malcolm Knapp Research Forest in Maple Ridge, B.C. for approximately one year, to examine the development, species, and sequence of invertebrates associated with the carrion. An invertebrate successional database was created for pond and stream habitats for potential use in estimating time of submergence in water related death investigations. Analysis has shown that a predictable succession of invertebrates colonize the carrion. However, whether or not this succession is carrion dependent or seasonal is unknown. There is a difference in the species composition between pond and stream habitats. Habitats influence invertebrate fauna, therefore, species colonizing carrion are habitat-specific. In both habitats, no one organism can determine time of submergence alone. Decompositional descriptions from this research were compared with 15 freshwater related death investigations. Similarities were seen in the earlier decompositional characteristics including bloat, discoloration, and nail shedding; however, the human descriptions were so vague that they had little value in determining time of submergence and hence time of death.

The influence of clothing and wrapping on carcass decomposition and arthropod succession during the warmer seasons in Central South Africa.

Abstract:  The influence of clothing and wrapping on carcass decomposition and arthropod succession was investigated to provide data to enable estimated postmortem interval in homicide investigations. Six pig carcasses, Sus scrofa, were divided into three sample groups, each with a clothed carcass wrapped and a carcass wrapped with no clothes. Two more carcasses, one with no clothes or wrapping, the other with clothes and no wrapping were used as controls. The clothed or wrapped carcasses had larger visible maggot masses, which moved more freely and these carcasses took longer to dry out. The blow fly maggot masses were dominated by Chrysomya marginalis and Chrysomya albiceps. Oviposition occurred simultaneously on all carcasses. High temperatures in one case caused significant maggot mortality. The Coleoptera community was dominated by Silphidae, Thanathopilus micans larvae, Dermestidae, Dermestes maculatus adults and larvae, and Cleridae, Necrobia rufipes.

Individualization and Enamel Histology: A Case Report in Forensic Anthropology

The cranium of a native Indian child about six years old was found in 1979 near Taseko River, British Columbia, Canada. While the remains matched the report of a child missing for eight years in terms of race, age at death, locale, and elapsed time since death, the cranium and dentition were basically unidentifiable because of the claimed lack of medical or dental history. There was no dental work, and the parents were unknown or dead. We report the presence, in the dental enamel of the primary and secondary dentition, of stress markers, termed striae of Retzius, whose locations correspond well with anecdotal reports and recently discovered medical records which describe the timing of specific episodes of stress. The enhanced probability of personal identification from dental histological stress markers is evaluated.

Arthropods of Forensic Importance on Pig Carrion in the Coahuilan Semidesert, Mexico

Abstract:  This is the first report of an ongoing research to establish a sarcosaprophagous arthropod database in the Coahuilan semidesert. Seven pigs (Sus scrofa L.) were used as human models to determine succession in an open urban area during the 2007 winter–spring period. Arthropods were collected manually and from pitfall traps. Carcass biomass loss, as well as arthropod colonization, was recorded during 71 days postmortem. Five decomposition stages were identified during which most abundant orders were found to be Diptera, Coleoptera, and Hymenoptera. Lucilia sericata (Meigen), Chrysomya rufifacies (Macquart), Necrobia rufipes (DeGeer), Dermestes maculatus (DeGeer), Pheidole hyatti Emery, and Pogonomyrmex rugosus Emery stood out as dominant species.