Quantifying the Temperature of Maggot Masses and its Relationship to Decomposition

Numerous Calliphoridae species have been observed to form larval aggregations during the feeding stage of development, resulting in localized increases in temperature. This study investigates the relationship between maggot numbers in a mass and heat generation. Single-species aggregations (Lucilia sericata) of various sizes (50–2500 individuals) were reared in the laboratory at a constant ambient temperature of 22°C. Internal mass temperatures were recorded every 5 min throughout the feeding stage of development. Results showed that mass temperatures increased with mass numbers (p-value < 0.001), ranging from 2.5 to 14°C above ambient. A minimum mass size of 1200 produced overall temperatures that were significantly warmer than ambient, diverging away from 22°C after c. 26 h. These results indicate that the microclimate of a mass has the potential to differ significantly from ambient, which may be influencing larval development rates and should therefore be factored into mPMI estimates to increase accuracy

Determining an accurate method for estimating the post-mortem interval of decomposed remains found in a temperate Australian environment

Estimating the post-mortem interval (PMI) is one of the most important determinations to make in a forensic investigation. However, at present, an accurate and reliable forensic anthropological method for estimating the PMI, based on the gross morphological changes occurring during decomposition, is currently unavailable. This is due to a multitude of variables influencing the rate and processes of decomposition in any given environment. Forensic anthropologists have traditionally relied on their knowledge and experience of the decomposition stages to make an assessment of the time since death. However, recently new, quantitative methods that are not solely based on the anthropologists observations, have been developed in a number of regions that have been proposed to accurately determine the PMI based on the observed decomposition changes alongside important taphonomic variables. The aim of the current study was to examine and document the decomposition process of pig carcasses, as an analogue for human remains, in the summer and winter climate of the Greater Western Sydney region. Secondly, the study aimed to evaluate the accuracy and replicability of the Megyesi et al. [1] ADD method, the Marhoff et al. [2] formula and the Vass [3] universal PMI formula, for their applicability as PMI methods in this region. Thirdly, should the methods mentioned above fail to accurately determine the PMI of remains within this region, a new method for PMI determinations will be created based on the observed decomposition changes and the most influential taphonomic variables affecting decay rates within the Greater Western Sydney region. Over an 18 month period, from June 2014 to March 2016, four experimental trials were undertaken: two summer trials and two winter trials. Eight adult pig carcasses per trial were left to decompose naturally on a soil surface at Western Sydney University’s Hawkesbury campus. During each trial, four carcasses were left to decompose in the shade under the canopy of trees and the other four carcasses were deposited in the open, with direct exposure to the sun. This was to examine the differences in decay rates between a sun and shaded microclimate. The published methods [1-3] and their associated scoring protocols were applied to determine the PMI of the remains. Through linear mixed modelling, the variation between the true PMI and the estimated PMI. The results showed that of the three methods validated in the present study, none could accurately determine the PMI in the Greater Western Sydney region. The Vass [3] formula overestimated the PMI during the winter trials but underestimated the PMI of the summer remains. The Megyesi et al. [1] and Marhoff et al. [2] methods were both found to underestimate the PMI when they were applied during the winter but overestimated the PMI when they were applied during the summer. As it was found that the currently published protocols for PMI estimates could not accurately determine the PMI of remains found within this region, a new method (the Marhoff-Beard method) for PMI determinations specific to the Western Sydney region was created. Using the degree of soft tissue decomposition observed at the time of discovery alongside the climatic variables humidity, wind speed, and rainfall, new regression equations were created. To determine if the new Marhoff-Beard formulae were accurately estimating the PMI for the Western Sydney region, the method was validated retrospectively from photographs of pig and human remains, and was applied longitudinally from the start to the end of the decomposition process on a donated human body. The validation showed this new method can accurately determine the PMI in a Western Sydney winter and summer climate and results were comparable when it was applied to both human remains and pig carcasses. The method performed consistently well during the fresh and early decomposition stages with a maximum error of eight days. As the remains dried and progressed through the advanced and skeletonisation stages, the accuracy of the method became compromised. It is likely the Marhoff-Beard method failed after this time point, as the decomposition process during the later stages is affected by further variables which were not accounted for by this method. Continued testing of the Marhoff-Beard method for PMI determinations should be undertaken both within this region and other temperate Australian locations. It should also be determined what variables are affecting decay rates during the more advanced stages of decomposition as this will help refine the PMI formula for its use during these stages

Forensic and ecological perspectives on insect succession on vertebrate remains

Entomological evidence is commonly used to estimate a post-mortem interval (PMI) in medicolegal investigations of deceased individuals. A PMI from insect-derived data can be estimated by either examining the thermal development rates of larvae or analysing the carrion insect succession process. The larval development method is well-established and reliable, while the succession method is less reliable as it depends on the predictable sequences of species arriving at a cadaver, which is a highly variable process. The effect of abiotic factors such as temperature and season on succession have been well documented, however the role of biotic factors has received far less attention. For the succession method to be reliably applied to forensic casework, a complete knowledge of all factors driving successional changes in insect communities needs to be known to identify and understand sources of variation. Parallel to developments in forensic science, carrion ecologists have begun to quantify the biological sources of variation in carrion insect succession and identify the role carrion plays in ecosystem function. Importantly, the carrion resource and associated necrobiome have been identified as important ecological drivers of variation in carrion insect succession. Yet these ecological approaches and techniques have yet to be transferred to forensic entomology. For example, pigs are often used as substitutes for human cadavers in forensic entomology despite the relatively unknown effect of cadaver type on carrion insect succession. There is great potential, therefore, to examine how developments in ecology might be used to advance forensic entomology. This thesis aims to learn from carrion ecology to advance forensic entomology by exploring ecological perspectives on how biotic factors such as cadaver type, carrion resource and species interactions drive variation in carrion insect succession. To do this, I conducted an innovative, multi-season experiment using pig and human cadavers at the Australian Facility for Taphonomic Experimental Research (AFTER)

Detection of Larval Aggregations Using a Drone Mounted Thermal Imaging Camera

When a body’s temperature reaches ambient temperature after death, remote detection of the body can become difficult. At this point, useful search tactics include the use of cadaver dogs, search parties and aerial imaging devices, all of which can be costly and time-consuming for every day law enforcement use. This study investigated the potential of a novel search technique in which a small, unmanned aerial system (drone) mounted with a forward-looking infrared radar (FLIR) was utilized to detect decomposing animal carcasses via the heat generated by associated Diptera larval aggregations. Hot water baths were utilized as analogs for larval aggregations in order to simulate varying conditions that could be encountered during a search and recovery mission, such as different sized aggregations and varying differences in temperature between aggregations and the environment. Animal carcasses were also utilized to determine the effectiveness of this search technique within the Connecticut region based on the formation of larval aggregations and the associated detection of the carcass on the days following its placement. While this research demonstrated that a thermal drone could successfully detect larval aggregations associated with a decomposing carcass, it also demonstrated that there are limitations to when or how this technique can be implemented during a search and recovery mission. An increase in drone height limited the capability of detection due to the masking of the hot water analog’s and carcass’s thermal signature by the surrounding environment, with a smaller heat source experiencing greater masking effects. Detection and accurate location of larval aggregations was also more likely to occur when there was minimal wind and sunlight at the time of deployment, and when ambient temperature was ideal for larval growth and development. Ultimately, the successful detection of larval aggregations was dependent upon the ability of the drone operator to understand how these factors can affect detection and how to adjust search parameters to optimize the success of this search technique

The Effect of Various Coverings on the Rate of Human Decomposition

A multitude of factors can affect the decomposition process, increasing or decreasing its rate. Some of the most frequently observed variables are temperature, moisture, insect activity, and sun or shade exposure. Coverings can impact the decomposition process, and are found frequently in forensic cases. In a survey of New Mexico cases, Komar (2003) reported that sixteen individuals were found wrapped in plastic, and twenty were noted as wrapped in a cloth or blanket. In a survey conducted of eighty-seven cases, fifty-four of the bodies were wrapped in some type of covering. Plastic was most common, but a variety was noted, including rugs, sleeping bags, and blankets, (Manhein, 1997). In order to document how coverings affect early decomposition an experiment was designed to mimic a forensic setting. Three human cadavers were used in each of two repetitions of this experiment. Two of the cadavers were covered, one in plastic tarp, the other in a cotton blanket, while the third was left uncovered as a control. The selection of materials was based on case reports of cadavers wrapped in plastic and blankets (Komar, 2003, Derrick, 2007 personal communication). Demographic and environmental variation between individuals was kept to a minimum. Data collected included daily minimum and maximum temperatures and two daily temperature point comparisons. The bodies remained covered for thirty days during this data collection. At the end of that period, the bodies were uncovered and the amount of decomposition was recorded

A Comparison of Human and Domestic Pig Decomposition Using Multivariate Methods

Animal proxies are frequently used to substitute for human remains in decomposition studies. Domestic pigs have become the most commonly used nonhuman proxy due to an assumed similarity in decomposition progression to humans. This dissertation directly compares decomposition patterns along morphological indicators, insect activity and scavenging to assess if decomposition between humans and domestic pigs is similar enough such that data produced from a pig model can accurately predict human patterns. This study examines 15 human donors to 15 domestic pigs across three seasons. The data are analyzed with multivariate methods, including hierarchical linear modeling and dynamic linear regression time series analysis. The results of this study suggest that when examining decomposition as an entire complex process, patterns differ between domestic pigs and humans. Individual similarities in specific variables do exist, but the overall patterns differ between species to an extent that pigs cannot substitute for humans in all taphonomic and decomposition research, especially where the goal is to improve estimations of the postmortem interval

Density and Mass Effect on the Development of Phormia regina

Forensic entomology is the application of the study of arthropods to the criminal justice system. This is primarily done through the development of a post mortem interval (PMI) based the insect evidence present. A practitioner must be able to determine the age of the insect through temperature data. One factor influencing the temperature dependent development is gregarious behavior. Current literature describes a faster development rate due to an increase in feeding efficiency and temperatures produced by this aggregate. However, there is very little literature defining a minimum number needed to induce this effect and little to none on it for Phormia regina. Two experiments were done to explore the effect of aggregation on P. regina juveniles. Both experiments used growth chambers set to 25°C and egg masses from lab reared colonies. The first experiment used two chambers with differing densities of larvae at 25, 50, 100, and 200 in 490ml plastic containers with 2cm of pine shavings. Larvae were reared on 2g of liver in 29.5ml plastic cups in the containers and liver was added as needed. Each container was subsampled with replacement every day to check the development of the larvae (10-25%) until adult eclosion. Aggregate temperatures were checked with a digital heat thermometer gun (TES) and probe throughout the duration of the experiment. No significant difference in development was observed. The mass temperatures in experiment one did not cause a decrease in development time as reported by the literature and the 100 counts had a higher average than the 200s. Experiment two was designed to explore this by increasing the space provided from a 490 ml container to a 1.42L one and to increase the feeding cup size from 29.5ml to 88.7ml. 25 and 200 larvae were provided 5g of liver to feed on initially.. Development times were significant longer for the 200 counts in the third instar and caused a downstream effect. Advisor: Leon G. Higle

Nutrient and moisture transfer to insect consumers and soil during vertebrate decomposition

Decomposition of organic matter leads to the redistribution of nutrients to organisms and the environment. Yet knowledge of this process has focused largely on plant-derived organic matter, with little known about relative quantities of nutrients and moisture transferred from decomposing animal remains to insect consumers and soil. We used a replicated and spatially blocked experiment to quantify the moisture, carbon, nitrogen, and phosphorous content of rabbit carcasses, maggot consumers, and soil over 20 days of decomposition. We found that maggot biomass reached 22% of the fresh rabbit carcass, or 39% of the consumable soft tissues. Maggots were comprised of 68% moisture, and their dry mass was comprised of 25% carbon, 4.9% nitrogen, and 0.8% phosphorous. Soils accumulated approximately 12.9% of the total carcass moisture, but only 0.7% of the carcass dry mass. The largest quantity of carcass mass loss was attributable to evaporation of moisture to the atmosphere (45%). Approximately 9% of the initial carcass mass was left as unconsumed remains. Our study provides estimates of the quantities of nutrients moving from vertebrate carcasses to insect consumers and soil. This knowledge is critical to scaling up the effects of carcasses and to developing our understanding of their role in biogeochemical cycling in ecosystems

Insect Signature Indicating Corpse Movement from Urban to Rural Areas of Northeast Ohio

The distribution of insects geographically may provide evidence that indicates the movement of human remains from one location to another. The aims of this study were: (1) to observe insect succession in an urban and rural area in northeastern Ohio to document differences in the entomofaunal succession, and (2) to determine if there is an insect signature associated with a body moved from an urban to a rural area. It was hypothesized that there would be a difference in species composition between the urban and rural sites and the body moved would retain insect evidence indicating initial exposure to an urban insect community. The insect signature of a moved corpse should differ from that of the urban and rural corpses. Six 12-19 kg domestic pig carcasses were obtained and placed in the following locations: two in a rural area of Cuyahoga County, and four in an urban area on Cleveland State University campus. After 24 hours, two of the carcasses from the urban location were moved to the rural location. Each carcass was sampled by hand sorting, aerial sweep netting and pitfall traps from 16 June 2009 to 1 August 2009. Most of the specimens were collected within the first four weeks of the study and included both adult and larval samples. All three carcass types supported a similar array of blow flies (Diptera: Calliphoridae) and beetles (Coleoptera). The dominant calliphorid, Phormia regina, represented approximately 66 of all specimens collected and was similarly represented on all carcass types. Although there were a few species unique to the urban or rural treatments, statistically there was no significant difference in insect composition between the treatments. Our analysis revealed that although species dominance and presence/absence of taxa may not indicate body movement in northeast Ohio, it does provide a database of forensically important insects which may be useful in future investigation