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Forensic Science International 176 (2008) 217–223 www.elsevier.com/locate/forsciint

A preliminary investigation of colonisation and succession on remains in New Zealand Terry L. Eberhardt a,*, Douglas A. Elliot b a The University of Auckland, Department of Chemistry, Forensic Science Programme, Building 301, Level 5, 23 Symonds St., Auckland, New Zealand b Institute of Environmental Science and Research Limited (ESR), A Crown Research Institute and The University of Auckland, Forensic Science Programme, New Zealand Received 22 May 2006; received in revised form 25 July 2006; accepted 20 September 2007 Available online 21 February 2008

Abstract A preliminary, systematic field study on the process of decomposition and associated was conducted, for the first time, in New Zealand. Using pig carcasses as an model for human decomposition, insect colonisation and succession was monitored in three different habitats in the Auckland region where remains are likely to be found. A significant difference in the rates of decomposition was found among the three different habitats of an open field, coastal sand dune area and native bush during the autumn/winter season. The primary colonisers of all carcasses were stygia Fabricius (), Chrysomya rufifacies Macquart (Calliphoridae) and Hydrotaea rostrata Robineau-Desvoidy (). Two species were identified as possible representatives of the habitats in which they were found; sp. (Fanniidae) in the open field habitat and Calliphora hilli Patton (Calliphoridae) in the native bush habitat. Also identified was Sylvicola sp. () as a possible indicator of damp habitats as well as a likely indicator of a longer postmortem interval. This preliminary investigation presents a broad outline of the insects associated with remains and the order in which they appear in the Auckland region. # 2007 Elsevier Ireland Ltd. All rights reserved.

Keywords: ; Insect succession; Decomposition; Postmortem interval

1. Introduction were most likely laid can be estimated. This interval of time provides the minimum time elapsed since flies first had access Forensic entomology is the application of the study of insect to the body and is based on the premise that the time required biology to criminal matters. The utilisation of insects in for larval development is predictable for each species of fly. forensic entomology is primarily associated with death The second method is based on the biological principle of investigations. However, it is not restricted to such events succession, where the colonisation of remains, as an ephemeral and may be used to determine the location of an incident [1,2], habitat, occurs in a reasonably predictable sequence. Succes- the presence and time of infliction of wounds [3], the length of a sional stages are represented by the variety of insect species period of neglect in the elderly or children [4], and the detection present at a particular time. This diversity is then compared to of drugs and poisons [5,6]. known successional patterns for that geographic area or habitat. In determining a postmortem interval, which is defined as The time required for the diversity of species to become as the time elapsed between death and discovery, insects provide established as they were at the time of discovery represents the evidence by two main methods. The first method is based on the estimated postmortem interval. age of fly larvae, as flies are the primary colonisers of a corpse. Many different variables may have an effect on the amount By determining the age of the larvae found with a corpse and of time that has elapsed since death. Ambient factors such as then using retrospective calculation, the time when the eggs temperature, local weather conditions and the surrounding habitat can have an influence on the length of the postmortem interval. Other influential factors include the season, body * Corresponding author. Tel.: +64 9 815 3670; fax: +64 9 849 6046. deposition (e.g. burial, exposed or indoors), and overall E-mail address: [email protected] (T.L. Eberhardt). geographical location. These variables can each have a

0379-0738/$ – see front matter # 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.forsciint.2007.09.010 218 T.L. Eberhardt, D.A. Elliot / Forensic Science International 176 (2008) 217–223 different effect and may combine in different ways at a which the dorsal aorta was cut to ensure death by internal exsanguination. particular crime scene. If the variables are not considered, they After death, the carcasses were sealed within plastic bags and transported to the study sites. may have a deleterious effect on the accuracy of a postmortem Three pig carcasses were placed 50 m apart in each habitat; two of which interval estimate. served as the research carcasses and one of which served as a control from Previous related work conducted between 1981 and 1983 in which no samples were collected. The control carcass was used to determine New Zealand involved the collection of insects associated with what, if any, disturbance was caused by the continual visitation and collection of human remains received for autopsy in Auckland [7]. The insects. Each carcass was dressed in a cotton T-shirt and underwear (modelling a common homicide scenario where the victim is clothed), then placed within a research presented here however, is the first systematic field chicken wire cage. The cage had a hinged lid and front panel to allow for access experiment to be conducted in New Zealand and aims to to the carcass and was constructed using PVC piping (2.5 cm) as the frame, enhance the information currently used to make an estimate of welded wire mesh (1 cm) as the base and 2.5 cm chicken wire as the sides and the postmortem interval based on insect evidence. Conducted top of the cage. This cage design ensured that the carcass would be in full during the autumn/winter season, the aims of this study were: contact with the ground and allowed for full environmental exposure while preventing scavenging from in the area. No sign of animal or human firstly, to observe and record insect species involved in the disturbance was noted during the study. primary colonisation of remains and their general rate of Weather stations, consisting of a maximum/minimum thermometer and a development in a natural setting; secondly, to observe and rain gauge were erected at each of the habitat sites. Weather data were collected record the order in which different insects appear and utilise the during each site visit for the duration of the study. However, the comparison of remains (succession) and; thirdly, to compare the process as it weather between the three habitats was restricted to consideration of the first 3 weeks, as site visits after this time decreased in frequency. Comparison of the occurs in three different habitats. To accomplish these aims, this values collected in the later part of this study would be inappropriate as the field experiment used pig carcasses as an animal model to values were cumulative and would therefore not accurately reflect the daily simulate human decomposition in three different habitats in the temperatures and rainfall experienced in the habitat. Auckland region. The study sites were visited 6 days a week for the first 3 weeks and every New Zealand is comprised of two main islands and several other day for the following 2 weeks. Site visits then tapered off until the last day of observation, 128 days after death. During each visit, the state of the carcass, smaller islands. The city of Auckland is located on the North weather conditions and insect activity were observed and recorded. A photo- 0 0 Island at 36851 S latitude and 174845 E longitude. The graphic record was also maintained for the duration of the study. Auckland region experiences a mild temperate climate where Representative samples of insects were collected from on, in and under the the average daily autumn temperature (March, April and May) carcasses and by sweep net above the carcasses to ensure as many different is 16 8C, with an average daily maximum temperature of 20 8C species as possible were collected. Samples of eggs and fly larvae were divided in two where half were killed at the site by immersion in near-boiling water and and an average daily minimum temperature of 12 8C. The half were taken to the laboratory for rearing. The rearing of larvae was for average daily winter temperature (June, July and August) is confirmatory identification purposes. 11 8C, with an average daily maximum of 15 8C and an average daily minimum of 7.5 8C. There is no snow and frost is uncommon. 3. Results

Five general stages of decomposition, modified from 2. Materials and methods descriptions provided by Goff [9], were identified. These Three different habitat sites were chosen based on the most common stages are subjective rather than discrete changes and are areas where a body is likely to be found in the Auckland region. The first generally accepted as artificial boundaries placed on a continual habitat was an open field consisting of mixed grasses, where intermittent process for the purposes of description [12–14]. The stages grazing by sheep and cattle is the predominant land activity. This site were named fresh, bloated, active decay, post-decay, and provided maximum environmental exposure. The second habitat chosen was a coastal sand dune area. The study sites in this habitat were located skeletal. For the purposes of this study, the fresh stage was approximately 1 km from the ocean and were partially shaded by low considered to be from the moment of death to the onset of shrubs (young manuka trees, Leptospermum sp.). The third habitat chosen bloating. The active decay stage was identified as when the was an area of native bush. The predominant vegetation in this area consists carcass deflated until most of the flesh from the carcass was of cabbage trees (Cordyline australis), manuka trees (Leptospermum sp.) consumed by larvae. The post-decay stage was indicated when and New Zealand flax (Phorium tenax), with a canopy approximately 10– 15 m high and a sandy soil covered with organic debris. This site provided the carcass was reduced to skin, cartilage and bone. The skeletal minimal sun exposure. stage was defined by the absence of flesh with only hair and The animal model used for this study was the domestic pig (Sus scrofa bones remaining. For all habitats, no disturbance in the process Linnaeus). The domestic pig has gastro-intestinal fauna and skin similar to of decomposition resulting from the continual visitation and humans and the size of the pig used in such studies is equivalent to the size of the collection of insects was detected between the control and average human torso [8,9]. The use of pigs is also much less controversial and more easily controlled, in terms of experimental design, comparison and research carcasses. continuity, than the use of properly obtained human corpses [10,11]. While As a preliminary investigation, the focus of the data an attempt was made to acquire pigs approximately 23 kg in weight, the collection was on the overall trends in species presence and recommended weight for this type of study [11], the weights obtained ranged abundance. Of primary interest were the species of Diptera that from 14.5 to 29 kg. colonised the remains and the order in which they appeared. Approval for the use of pigs as an animal model in this study was obtained from the Animal Ethics Committee at the University of Auckland (AEC/02/ Therefore, only those species of Diptera colonising the remains, 2002/R13). Each pig was killed by a veterinarian using a captive-bolt pistol indicating their potential for forensic use in New Zealand, are fired into the skull followed by an immediate intercostal incision through presented below. The results are presented chronologically for T.L. Eberhardt, D.A. Elliot / Forensic Science International 176 (2008) 217–223 219 each habitat. The observed pattern of succession is presented in Chrysomya rufifacies Macquart (Calliphoridae) and table format and while not an exhaustive listing of species Hydrotaea rostrata Robineau-Desvoidy (Muscidae) adults found associated with the remains, includes members of were both first observed on day 1. Ch. rufifacies adults were Hymenoptera and Coleoptera demonstrating the overall trends observed and collected at the remains until day 15 and larvae in the pattern of succession. were present from day 13 to 47. Adult H. rostrata were recoveredfromtheremainsfromday1untilday19.TheH. 3.1. Open field habitat rostrata larvae however, had both a delayed and prolonged presence on the remains and were observed and collected The open field habitat had an average daily maximum fromday20to92. temperature of 19.4 8C and an average daily minimum Adult Lucilia sericata Meigen (Calliphoridae) were not temperature of 11.1 8C. The average daily rainfall recorded found in the aerial sweep net collections in this habitat; during the first 3 weeks in this habitat was 3.0 mm/day. however, L. sericata was reared from one collection sample, The carcasses in this habitat had a similar length fresh stage consisting of new eggs found on one carcass, on day 23. of0–1days,withday0referring to the day of death and In this habitat alone were Fannia sp. (Fanniidae) recovered. placement of the pig carcass in the habitat. The bloat stage was Adults were not observed or collected from the remains; observed from day 1 to 17, with one carcass remaining bloated however, larvae were first recovered on day 32 and were present until 36 days after death. In this habitat, the end of the bloat until day 92. stage was difficult to ascertain as there was not the abrupt species other than those in the predominant Calliphor- visual cue of deflation as observed in the other two habitats. idae and Muscidae families were observed and collected from After the bloat stage, the active decay stage was observed at the carcasses and include members from the families two of the carcasses from 19 to 45 days after death. After the and Anisopodidae. Adults in the Psychodidae 36-day bloat stage experienced by one of the carcasses, little family were first observed on day 23 and then recorded as change was seen at this carcass on subsequent visits. The absent until day 39. Psychodidae larvae were first collected on skeletal stage was not observed in this habitat as the carcasses day 52 and were present in large numbers from day 63 to 77. retained body tissue until the termination of the study, 126 days From day 77 until the end of this study there was an increase in after death. adult Psychodidae numbers likely reflecting the emergence of The first fly species to arrive at each of the three carcasses in new flies. Sylvicola sp. (Anisopodidae) were observed and the open field habitat was Calliphora stygia Fabricius collected from the remains late in the decomposition process. (Calliphoridae). Adults were observed and collected from Adults were first found on day 57 and larvae were first the remains from day 0 to 17. C. stygia larvae were first recovered on day 99. observed on day 1 and were present until day 27, with further The overall relative abundance and species succession for observations and collections on days 47 and 77. the open field habitat is visualised in Table 1.

Table 1 Open field habitat, relative abundance over time of insects observed and recovered from study carcasses 220 T.L. Eberhardt, D.A. Elliot / Forensic Science International 176 (2008) 217–223

3.2. Coastal sand dune habitat only recorded on 2 subsequent days, 61 and 68. No larvae were recovered. The coastal sand dune habitat was the warmest with an Larvae of the family Piophilidae were observed and collected average daily maximum temperature of 21.4 8C and an average at one carcass in this habitat. A total of 5 larvae were observed on daily minimum temperature of 13.5 8C. The average daily days 82, 90 and 110 and of the two collected, neither was rainfall in this habitat was 1.4 mm/day during the first 3 weeks. successfully reared preventing further identification. As in the open field habitat, the fresh stage was observed The overall relative abundance and species succession for from day 0 to 1. The bloat stage was recorded from day 2 until the coastal sand dune habitat is visualised in Table 2. day 5 at one carcass and until day 7 at the remaining two carcasses. The active decay stage was observed from 6 to 15 3.3. Native bush habitat days after death and the post-decay stage was recorded until the termination of the experiment (124 days) with no skeletal stage The native bush habitat had an average daily maximum observed at any of the carcasses. temperature of 18.0 8C and an average daily minimum Calliphora stygia and Chrysomya rufifacies were the first temperature of 13.0 8C. The average daily rainfall recorded species attracted to and collected from the remains in this during the first 3 weeks of exposure was 0.4 mm/day. habitat. Adult C. stygia were present from day 0 until day 24. Due to a delay of approximately 4 h in setting up this habitat Larvae were first observed on day 2 and were present until day study site, the carcasses appeared bloated when removed from 15. Adult Ch. rufifacies were observed and collected from day 0 their plastic bags, therefore, the fresh stage was not observed in to 15. Ch. rufifacies larvae were not present until day 9 and were this habitat. The bloat stage was observed from day 0 to 7 for observed and collected until day 34. two of the carcasses and until day 9 for the third carcass. The Adult Hydrotaea rostrata were present at the remains from active decay stage was recorded from day 9 to 12 for two of the day 0 until day 34. The larvae were again present for a carcasses and from day 9 to 14 for the third. The post-decay prolonged period, from day 11 to 82. stage was observed for the remainder of the experiment with the One adult specimen of Calliphora quadrimaculata Swe- exception of one carcass observed in the skeletal stage at 124 derus (Calliphoridae), a species endemic to New Zealand, was days after death, the last day of the study. collected in an aerial sweep above one carcass in this habitat. Calliphora stygia was once again the first adult fly to arrive This species was not observed or collected again and larvae of at the carcasses. In this habitat however, Calliphora hilli Patton this species were not recovered from any of the carcasses in any (Calliphoridae) may also have been present as this species, of the habitats. while not recovered in aerial sweep netting on day 0, was reared Species recovered during the later stages of decomposition from initial larval collections. Adult C. stygia and C. hilli were include members of the families Sphaeroceridae, Psychodidae recorded from day 0 until day 24 with larvae observed and and Piophilidae. Adult Sphaeroceridae were first observed and collected from day 2 until day 15. Adult Ch. rufifacies were collected on day 25 and their presence was again recorded from observed from day 2 to 14, and larvae were observed and day 55 to 124. No larvae of this family were observed or collected from day 10 to 18 with additional observations on collected. Adult Psychodidae, first observed on day 48, were days 21 and 27.

Table 2 Coastal sand dune habitat, relative abundance over time of insects observed and recovered from study carcasses T.L. Eberhardt, D.A. Elliot / Forensic Science International 176 (2008) 217–223 221

Table 3 Native bush habitat, relative abundance over time of insects observed and recovered from study carcasses

Adult H. rostrata were recorded from day 2 until day 31. The the limited insect activity observed in the open field habitat. larvae once again demonstrated a delayed appearance and The influence of insect activity, primarily blow flies, on the prolonged presence on the remains from day 13 until day 82. rate of decomposition has been demonstrated in studies where Of special note is one sample collected on day 2 which insect activity was inhibited [15], the case study of a wrapped yielded one individual Calliphora vicina Robineau-Desvoidy corpse [16] and the investigation of the effect of burial on (Calliphoridae). This was the only specimen collected during decomposition [17–19]. As the carcasses in all habitats were this research. fully exposed to the environment and easily accessible to Members of the families Phoridae and Sphaeroceridae were insects, it is likely that colonisation of the carcasses in the also recorded intermittently from day 18 until day 124. The open field habitat was adversely affected by the weather, rain families were unable to be differentiated in the field and as both in particular, resulting in an overall slower rate of were present in collections they are presented together. Adult decomposition. Psychodidae were first observed on day 24 and were present The most significant weather difference between the three between days 41 and 124. habitats was that of rainfall, with the open field habitat Similar to the open field habitat, Anisopodidae (Sylvicola experiencing a 3.0 mm/day average compared to the 1.4 and sp.) were also recovered late in the decomposition process. The 0.4 mm/day for the native bush and coastal sand dune habitats first adults were observed on day 52 and were then present respectively. This appears to have had an adverse affect on the sporadically from day 76 until day 124. Sylvicola sp. larvae insect colonisation of the carcasses in the open field habitat. were then observed and collected from day 82 until day 124. Interestingly, in comparison with work done by Shean et al. The overall relative abundance and species succession for [20] on differential decomposition in exposed versus shaded the native bush habitat is visualised in Table 3. carrion, our results demonstrate the reverse pattern. The open field habitat showed a significantly slower rate of decomposi- 4. Discussion tion although this site was fully exposed to the elements. The native bush habitat, which may be considered as shaded with While the overall rate of decomposition within a habitat was approximately 75% canopy cover, experienced a similar rate of similar, there was, however, a significant difference in the rate decomposition as the moderately exposed coastal sand dune of decomposition between habitats. The coastal sand dune area. This suggests that cloud cover and rainfall may have a habitat exhibited the fastest rate of decomposition, with the similar effect on decomposition and associated insect activity native bush habitat only slightly slower, whereas the open field as a shaded habitat. habitat exhibited a substantially slower rate. The colonisation of the carcasses in all habitats was This different rate of decomposition between habitats is primarily by C. stygia, Ch. rufifacies and H. rostrata and adults emphasised by the observations 15 days after death. Carcasses of these species were consistently observed as the first to arrive in the coastal sand dune and native bush habitats were in the at the carcasses. This suggests that these three species are the post-decay stage, whereas the carcasses in the open field primary colonisers of carrion in the autumn/winter season in the habitat were still in the bloat stage. Of particular interest was Auckland region. 222 T.L. Eberhardt, D.A. Elliot / Forensic Science International 176 (2008) 217–223

The colonisation of the carcasses was consistent in all Acknowledgements habitats with initial egg deposition at the head region and larval activity observed as progressing from the head to the anal Special thanks to Peter and Janet Coulson and the Royal region. Larval masses of C. stygia were the first to develop in all New Zealand Air Force for the use of their respective lands. We carcasses in all habitats in the chest and abdominal regions of would also like to extend our gratitude to Dr. Trevor K. Crosby the remains, followed by smaller larval masses of Ch. rufifacies. of Landcare Research New Zealand for his verification of insect Larvae of Ch. rufifacies were found in fewer numbers in the identifications. This research was funded in part by the Institute native bush and open field habitats than in the coastal sand dune of Environmental Science and Research Ltd. Capability habitat and suggest a preference for drier and warmer Development Fund and was conducted as partial fulfilment environments. This supposition is supported by Dear [21] of the requirements for an M.Sc. in Forensic Science at the who states that Ch. rufifacies is a known secondary agent of University of Auckland. in sheep, and appears to strike only in hot, dry weather. Smeeton et al. [7] suggest H. rostrata is ‘useless’ as a References forensic indicator as the authors found the species able to oviposit on remains of various ages. However, the delayed [1] M.L. Goff, Comparison of insect species associated with decomposing arrival of H. rostrata larvae during this research suggests a remains recovered inside dwellings and outdoors on the island of Oahu, possible use for establishing a minimum time elapsed estimate, Hawaii (USA), J. Forensic Sci. 36 (1991) 748–753. with the earliest observation of larvae on day 11 in the coastal [2] J.P.J. Webb, R.B. Loomis, M.B. Madon, S.G. 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Entomol. 9 experience and knowledge of the consulting entomologist. (1992) 237–243. With the successful completion of this preliminary investiga- [17] J.A. Payne, E.W. King, G. Beinhart, Arthropod succession and decom- tion however, a broad outline of the species associated with position of buried pigs, Nature 219 (1968) 1180–1181. remains and the order in which they appear has been described [18] B. Turner, P. Wiltshire, Experimental validation of forensic evidence: a for the Auckland region. Further research is currently underway study of the decomposition of buried pigs in a heavy clay soil, Forensic Sci. Int. 101 (1999) 113–122. to refine the details of this outline in order to enhance the [19] S.L. VanLaerhoven, G.S. Anderson, Insect succession on buried carrion in confidence and accuracy of estimating a postmortem interval two biogeoclimatic zones of British Columbia, J. Forensic Sci. 44 (1999) based on insect evidence in New Zealand. 32–43. T.L. Eberhardt, D.A. 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