Maggot Masses Research Articles

Infection risk associated with carnivore carcasses may govern trophic interactions between maggots and insectivorous passerine birds.

Infection risk by pathogenic agents motivates hosts to avoid using resources with high risks. This, in turn, results in increased availability of these resources for other species that are more tolerant of infections. For instance, carcasses of mammalian carnivores are frequently avoided by conspecific or closely related carnivores, allowing them to be almost exclusively used by maggots. This may lead to novel interactions with other species. This study investigated the consumption of maggots from carnivore carcasses by non-corvid passerines. We successfully monitored 66 raccoon carcasses in Hokkaido, Japan, from 2016 to 2019. Vertebrates only scavenged 14 carcasses before maggot dispersal; the other 52 carcasses produced abundant maggots that regularly fed at least 12 species of non-corvid passerines. Surprisingly, predation occurred at a distance from the carcasses, mainly after maggot dispersal for pupation, despite the higher efficiency of feeding on maggot masses on the carcasses. Birds are likely to reduce the potential risk of infection from the carcass and/or from maggots on the carcasses. Overall, only 1% of maggots were consumed. Our results suggest that necrophagous flies could benefit from the infection risk associated with carnivore carcasses, which may decrease scavenging by other carnivores and constrain maggot consumption by insectivorous birds.

Use of thermal drone in detection and assessment of larval mass temperature in decomposed rabbit carcasses.

Manual ground searches and cadaver dogs are traditional methods for locating remains, but they can be time- and resource-intensive, resulting in the decomposition of bodies and delay in victim identification. Therefore, thermal imaging has been proposed as a potentially useful tool for detecting remains based on their temperature. This study investigated the potential of a novel search technique of thermal drones to detect surface remains through the detection of maggot mass temperatures. Two trials were carried out at Selangor, Malaysia, each utilizing 12 healthy male Oryctolagus cuniculus European white rabbits and DJI Matrice 300 RTK drone China, equipped with a thermal camera; Zenmuse H20T to record the thermal imaging footage of the carcasses at various heights (15, 30, 60-100 m) for 14 days for each trial. Our results demonstrated that the larval masses and corresponding heat emissions were at their largest during the active decay stage; therefore, all the carcasses were observable in thermal images on day 5 and remained until day 7. Statistical analyses showed that (1) no statistically significant differences in thermal images between clothed and unclothed subjects (p > 0.05); (2) 15 m above ground level was proven to be the optimal height, as it showed the greatest contrast between the carcass heat signature and the background (p < 0.005). Our data suggested the potential window of detection of thermal signatures was detectable up to 7 days post-deposition. This could be an important guideline for the search and recovery teams for operational implementation in this tropical region.

Direct relationship between evapotranspiration rate (ETO) and vertebrate decomposition rate

When vertebrate scavenging is excluded, the Evapotranspiration Rate (ETo) of a given geographic region directly regulates the decomposition rate of unclothed vertebrate carrion, with any deviation attributed to insect activity. We conducted four decomposition experiments using pig carrion (Sus scrofa domesticus) over the span of two years (2018–2020) at a location in Davis, California. We used ETo, a variable that accounts for five climatic parameters (wind, temperature, humidity, solar radiation, and altitude) as the rate-determining variable of the decomposition process. We found ETo to have a strong (R2 = 0.98) predictive relationship with the decomposition rate. To account for maggot activity decomposing the carrion, we measured maggot weight in 2019 and 2020 using a novel method, and in 2020 we used FLIR imagery to measure maggot mass temperatures as a surrogate measurement of total maggot activity. Maggot activity was a significant predictor (p < 0.0001) of the decomposition rate, while maggot weight was not (p > 0.1). We hope to show the forensic entomology community the potential of using ETo. Future projects can incorporate ETo as a baseline to decomposition studies to determine if ETo remains the most accurate descriptor of decomposition and ultimately increase certainty in the Postmortem Interval (PMI).

Anoxia Tolerance in Four Forensically Important Calliphorid Species

Forensically important blow flies, Diptera: Calliphoridae, are among the first organisms to colonize carrion. After eggs hatch, the larvae of most blow fly species feed in an aggregation or “mass”. While in this mass larvae may experience periods of hypoxia/anoxia, but the tolerance of blow fly larvae to anoxic conditions is poorly studied. We tested the anoxia tolerance of four species of calliphorids (Calliphora vicina, Cochliomyia macellaria, Lucilia sericata, and Phormia regina), by examining actively feeding third-stage larvae across five temperatures. Experiments were conducted by exposing larvae to pure nitrogen environments and determining mortality at set time intervals. All species show significant linear relationships between survival time and temperature under anoxic conditions. Of species tested, C. macellaria had the greatest tolerance to anoxia (LT50 of 9 h at 20 °C). In contrast, C. vicina was the least tolerant (LT50 of 2.2 h at 40 °C). With all species, survivorship decreased with increasing temperature. Unlike many other insects tested in severe hypoxia, the larvae of the calliphorids tested, which included members of three subfamilies, were not tolerant of anoxic conditions. From these findings, it seems likely that hypoxia is a significant limitation for maggots in a maggot mass, particularly when the mass temperature is high (&gt;40 °C). Forensically, these data provide a limit on potential maggot survival on bodies that have been submerged or otherwise experience severe hypoxia before discovery.

Caught in the act: impact of Crematogaster cf. liengmei (Hymenoptera: Formicidae) necrophagous behavior on neonate pigs (Sus scrofa domesticus L.) in the Western Cape Province of South Africa.

Ants have been documented as part of the entomo-sarcosaprophagous community. They have been known to alter the process of carcass decomposition due to their ability to feed on fly eggs/larvae and create post-mortem skin injuries. However, studies on the impact of ants on decomposing carcasses are scarce, especially within the Western Cape Province of South Africa. This study was part of a research project that utilized two (2) neonate pig carcasses in each month of the year to establish baseline data on the insect species associated with decomposing carcasses in the Western Cape Province of South Africa. In the early spring (September 2020), mid-autumn (May 2021), and mid-winter (July 2021) trials respectively, several individuals of Crematogaster cf. liengmei colonized the pig carcasses shortly after deployment. There, they fed on the flesh of the carcasses and further inflicted bite marks and conspicuous post-mortem skin lesions. Following the reduction in the presence of Crematogaster cf. liengmei specifically in the mid-winter trial, non-vital bleeding was observed as a consequence of the skin lesions. In the early spring, mid- and late autumn (May 2021), and early (June 2021) and mid-winter trials respectively, Crematogaster cf. liengmei prevented the formation of large maggot masses, principally through the predation of fly eggs, larvae, and adults. The observations recorded in this study are of considerable importance in forensic investigations as the effect of the necrophagous behavior of Crematogaster cf. liengmei on decomposing remains can be misinterpreted by inexperienced investigators during crime scene investigations and may alter post-mortem interval estimations.

Developmental niche construction in necrophagous larval societies: Feeding facilitation can offset the costs of low ambient temperature

Abstract This study explored the trade‐offs between thermal regulation and aggregation, two key factors impacting blow fly (Diptera: Calliphoridae) larvae development. Recent works have demonstrated that necrophagous maggots engage in developmental niche construction, which provides adaptive benefits. First, each species has a preferential temperature, at which larvae grow fast and efficiently. Second, larvae are attracted by each other and aggregate in large maggot masses. These groups modify the local environment and facilitate the exodigestion process (niche construction by perturbation). However, aggregation and relocation towards thermal preferendum are not always compatible under field conditions, forcing larvae to make choices. To test the developmental consequences of such trade‐offs, 40 or 80 Lucilia sericata larvae were placed on a thermal gradient (from 22 to 48°C) with or without a captive aggregate of 40 larvae located at 22°C, and their development speed, size and survival were measured. A previous study showed that in such situation the free larvae alone relocated at 33°C, while in the presence of captive larvae they gathered with the captive group at 22°C. In the present developmental study, we observed that such 22°C aggregated larvae actually grew as fast as if they were at 33°C. This result shows that niche construction, here resulting from larval gregarism and feeding facilitation, can compensate for the physiological costs of low ambient temperature. This finding confirms that aggregation of necrophagous Diptera larvae is an efficient adaptation to the carrion environmental constraints and highlights the adaptive value of developmental niche construction.

Application of forward-looking infrared (FLIR) imaging from an unmanned aerial platform in the search for decomposing remains.

Traditional methods of cadaver detection in outdoor environments include manual ground search, cadaver dogs, and manned aerial reconnaissance during daylight. These methods have limitations; however, a potential low-cost alternative may be to employ thermal imaging equipment mounted on an unmanned aerial vehicle (UAV) to detect heat emitted by insect and bacterial activity on the decomposing remains. No studies have addressed the influence of wrappings on detection of maggot mass thermal signatures nor assessed thermal detection of smaller body fragments. We addressed these knowledge gaps by utilizing a two-phase experimental approach to explore thermal detection of carcasses using UAV-mounted infrared imaging. In Phase 1, pig body fragments were deposited on the surface or shallow buried. In Phase 2, whole pig carcasses were deposited in four conditions: on the surface uncovered, wrapped in plastic or carpet, or buried. Our results demonstrated that observable heat emissions from remains corresponded to peak insect activity during active decay and could be readily detected in uncovered whole carcasses and fragments. Although plastic and carpet wrappings partly impeded detection of insect heat signatures, these materials were clearly detectable themselves because of their contrast to the background ground surface. Thermal signatures of buried partial remains and disturbed gravesoil were also observed; however, the buried whole carcass transitioned to adipocere prior to the decay stage and without any insect colonization or heat signature. These data can inform operational implementation of this technique to complement existing search strategies to offer a robust, low-cost alternative for use where scene characteristics allow.

Identification of the Species Constituents of Maggot Populations Feeding on Decomposing Remains-Facilitation of the Determination of Post Mortem Interval and Time Since Tissue Infestation through Application of Machine Learning and Direct Analysis in Real Time-Mass Spectrometry.

The utilization of entomological specimens such as larvae (maggots) for the estimation of time since oviposition (i.e., egg laying) for post mortem interval determination, or for estimation of time since tissue infestation (in investigations of elder or child care neglect and animal abuse cases), requires accurate determination of insect species identity. Because the larvae of multiple species are visually highly similar and difficult to distinguish, it is customary for species determination of maggots to be made by rearing them to maturity so that the gross morphological features of the adult can be used to accurately identify the species. This is a time-consuming and resource-intensive process which also requires that the sample be viable. The situation is further complicated when the maggot mass being sampled is comprised of multiple species. Therefore, a method for accurate species identification, particularly for mixtures, is needed. It is demonstrated here that direct analysis in real time-high resolution mass spectrometric (DART-HRMS) analysis of ethanol suspensions containing combinations of maggots representing Calliphora vicina, Chrysomya rufifacies, Lucilia coeruleiviridis, L. sericata, Phormia regina, and Phoridae exhibit highly reproducible chemical signatures. An aggregated hierarchical conformal predictor applied to a hierarchical classification tree that was trained against the DART-HRMS data enabled, for the first time, multispecies identification of maggots in mixtures of two, three, four, five, and six species. The conformal predictor provided label specific regions with confidence limits between 80 and 99% for species identification. The study demonstrates a novel, rapid, facile, and powerful approach for identification of maggot species in field-derived samples.

Honey, Can You Take Out the Garbage Can? Modeling Weather Data for Cadavers Found Within Containers

To produce postmortem interval estimations, forensic experts are often required to model weather conditions prior to the discovery of a cadaver by linking records from a regional meteorological weather station and an on-site portable weather station. Sometimes, however, cadavers are concealed within containers that will not automatically conform to the ambient temperature, thus making modeling more complex. Here, we have examined the factors influencing the modeling of weather data for carcasses concealed in suitcases, trash cans, and sealable drums. Results showed that in situ temperature modeling was facilitated by the use of additive models accounting for the non-linear effect of the time of day due to delays in temperature oscillations between the meteorological weather station and the study site. The containers concealing a carcass tended to be warmer than the ambient air and increased in temperature with a delay when ambient air temperature was hot, especially for less permeable containers. Containers that allowed fly larvae or adults to access the carcass (i.e., suitcases and trash cans) exhibited higher temperatures at smaller postmortem interval values than sealed containers (i.e., drums), which was likely caused by a maggot mass effect. The data collected improve our understanding of the phenomena affecting the modeling of in situ temperature records and of the microhabitat of concealed carcasses. Based on the results, we stress that when forensic modeling involves two sequential steps (i.e., in situ temperature modeling followed by the use of insect developmental curves, decomposition scores, algor mortis equations, etc.), close attention should be given to the first step because its deficiency limits the quality of the predictions from the subsequent step.

Decomposition pattern and insect colonization in two cases of suicide by hanging

ABSTRACTHanging is one of the most common methods of suicide worldwide. Despite the high incidence, only a little knowledge about the pattern of cadaver colonization by insects on hanging corpse is available. Different types of hanging can alter the body decomposition process as well as the pattern and rate of insect colonization. Two case studies where the hanging occurred with a similar postmortem interval of 34 days are described. The two bodies showed different patterns of insect colonization and decomposition scored using the Total Body Score (TBS) and the TBS for hanging (TBShang). The first case was about the body of a 24-years-old male, with mummification of the unclothed upper anatomical parts. A TBS of 14 and a TBShang of 18 were assigned. The second body, belonging to a 15-years-old male, was found pre-skeletonized lying on the ground with the skull disarticulated. A TBS of 31 and a TBShang of 32 were assigned. Average temperatures of (21.5 ± 2.5) °C for the first body and (25.1 ± 2.7) °C for the second body were recorded in the 34 days preceding the bodies’ discovery for a total of 731 and 853 Accumulated Degree Days (ADD) respectively. According to previous studies, the different decomposition patterns were related to temperatures of exposition and to the diversity of arthropod community found on the bodies because of the different types of hanging: totally suspended vs. in contact with the soil. The limited insect activity caused by hanging explains the delay in decomposition of hanging bodies in which mummification can take place, especially on the upper body parts. In vertical body position, the body fluids accumulated in the lower body parts accelerating the desiccation of soft tissues on the upper parts. The effect of gravity can also explain the decrease of internal maggot mass as larvae easily fall from the hanging body to the drip zones below where they are unable to recolonize the body if totally suspended. Furthermore, in a hanging body a greater surface is exposed to wind and sun with a quicker skin drying preventing the additional Diptera colonization. This paper shows the weaknesses of scoring scales and regression models developed to predict ADD when irregular decomposition and mummification have not taken into account.

Thermoregulation behavior in necrophagous dipteran larvae

The forensic entomology is the use of insects to date the death. The forensic expert assessment is based on the development of necrophagous insects which are growing on the cadaver, to calculate their age and then estimate the Post-Mortem Interval. This development depends on a number of parameters like temperature, species or behavior. The French Forensic Taphonomy unit, the only expert team on the subject in France, works on the biology, physiology and ethology of the necrophagous insects. Their works are focused on thermoregulation behavior and thermal preferendum of maggot masses, aggregation phenomenon and social interaction or on food intake. These works are particularly of interest to understand the pre-social parameters and evolution strategies. More importantly, their aim is to better understand the development of necrophagous insects and, in fine, to improve the forensic expert assessment.

To eat or get heat: Behavioral trade-offs between thermoregulation and feeding in gregarious necrophagous larvae.

The thermoregulation behavior of Lucilia sericata larvae (Diptera: Calliphoridae), a necrophagous species that feeds on vertebrate cadavers, was investigated. These larvae require high heat incomes to develop, and can elevate temperatures by forming large aggregates. We hypothesized that L. sericata larvae should continue to feed at temperatures up to 38 °C, which can be reached inside larval masses. Thermal regulation behavior such as movement between a hot food spot and colder areas was also postulated. The hypotheses were tested by tracking for 1 h the activity of single, starved third instar larvae in a Petri dish containing 1 food spot (FS) that was heated to a constant temperature of 25 °C, 34°C or 38°C with an ambient temperature of 25 °C. The influence of previous conspecific activity in the food on larval behavior was also tested. The crops of larvae were dissected to monitor food content in the digestive systems. Based on relative crop measurements, larvae fed at all food temperatures, but temperature strongly affected larval behavior and kinematics. The total time spent by larvae in FS and the duration of each stay decreased at high FS temperature. Previous activity of conspecifics in the food slightly increased the time spent by larvae in FS and also decreased the average distance to FS. Therefore, necrophagous L. sericata larvae likely thermoregulate during normal feeding activities by adjusting to local fluctuations in temperature, particularly inside maggot masses. By maintaining a steady internal body temperature, larvae likely reduce their development time.

Helicopter thermal imaging for detecting insect infested cadavers

One of the most common techniques applied for searching living and even dead persons is the FLIR (Forward Looking Infrared) system fixed on an aircraft like e.g. a helicopter, visualizing the thermal patterns emitted from objects in the long-infrared spectrum. However, as body temperature cools down to ambient values within approximately 24h after death, it is common sense that searching for deceased persons can be just applied the first day post-mortem. We postulated that the insect larval masses on a decomposing body generate a heat which can be considerably higher than ambient temperatures for a period of several weeks and that such heat signatures might be used for locating insect infested human remains.We examined the thermal history of two 70 and 90kg heavy pig cadavers for 21days in May and June 2014 in Germany. Adult and immature insects on the carcasses were sampled daily. Temperatures were measured on and inside the cadavers, in selected maggot masses and at the surroundings. Thermal imaging from a helicopter using the FLIR system was performed at three different altitudes up to 1500ft. during seven day-flights and one night-flight.Insect colonization was dominated by blow flies (Diptera: Calliphoridae) which occurred almost immediately after placement of the cadavers. Larvae were noted first on day 2 and infestation of both cadavers was enormous with several thousand larvae each. After day 14 a first wave of post-feeding larvae left the carcasses for pupation. Body temperature of both cadavers ranged between 15°C and 35°C during the first two weeks of the experiment, while body surface temperatures peaked at about 45°C. Maggot masses temperatures reached values up to almost 25°C above ambient temperature. Detection of both cadavers by thermal imaging was possible on seven of the eight helicopter flights until day 21.

The Dynamic Maggot Mass Microbiome

Necrophagous insect studies have shown that decomposing vertebrate remains are an important ephemeral resource within an ecosystem. However, the microbes (e.g., bacteria and archaea) that were a part of the once living organism and the exogenous taxa that colonize this postmortem resource remain largely underexplored. Also, it is not well understood how these two kingdoms interact to recycle decaying biomass, an important mechanistic question for ecosystem function ecology. To better understand microbial community dynamics throughout decomposition, we used swine carcasses (N = 6) as models for mammalian postmortem decomposition to characterize epinecrotic microbial communities from: the abdominal skin of replicate carcasses; the internal microbiome of individual necrophagous dipteran larvae (maggots); and the microbiome of dipteran larval masses that had colonized the carcasses. Sampling occurred every 12 h for the duration of the decomposition process. We characterized these microbial communities over time using high-throughput 16S amplicon sequencing. The relative abundance of microbial taxa changed over decomposition as well as across sampling locations, suggesting significant interactions between the environment, microbes, and insect larvae. Maggot masses were represented by multiple blow fly species in each mass: Phormia regina (Meigen), Lucilia coeruleiviridis (Macquart), and Cochliomyia macellaria(F.). Relative abundance of these species within the mass also changed as decomposition progressed, suggesting the presence of certain Calliphoridae species within a mass may be associated with temporal shifts of the microbial communities. These results provide new insight into the community ecology of carrion decomposition by providing new data on interactions of microbes and dipteran larvae over time.

Heat accumulation and development rate of massed maggots of the sheep blowfly, Lucilia cuprina (Diptera: Calliphoridae)

Blowfly larvae aggregate on exposed carcasses and corpses and pass through three instars before wandering from the carcass and pupating. The developmental landmarks in this process can be used by forensic entomologists to estimate the time since the insects colonised the carcass, which sets a minimum post mortem interval. Large aggregations of feeding larvae generate a microclimate with temperatures up to 15°C above ambient conditions, which may accelerate larval development and affect forensic estimates of post-mortem intervals. This study investigated the effects of heat accumulated by maggot masses of Lucilia cuprina at aggregations of 20, 50 and 100 larvae, each at incubation temperatures of 18°C, 24°C and 30°C, using body length and life stage as developmental indicators. Aggregation temperatures reached up to 18.7°C above ambient temperature, with significant effects of both size and temperature of the aggregation on the development time of its larvae. Survivorship was highest for all life stages at 24°C, which is near the developmental optimum of L. cuprina. The results of this study provide a broadly applicable method of quantifying heat accumulation by aggregations of a wide range of species of forensic importance, and the results obtained from such studies will demonstrate that ambient temperature cannot be considered the only source of heat that blowfly larvae experience when they develop on a carcass. Neglect of temperatures within larval aggregations will result in an overestimation of post-mortem intervals and thus have far-reaching medicolegal consequences.

The entomology of perinatal investigations

Forensic entomology is the application of the study of insects to legal problems. The minimum time since death may be estimated for a deceased person by aging the oldest fly larvae (maggots) collected from the body. Degree of larval development is compared with known development rates at the estimated prevailing temperatures. The species composition of insects on the body is also characteristic at different times after death, and therefore useful for aging the body. Perinatal deaths present special difficulties to the entomologist because the body is easy to move, and may be repositioned more than once after death. This complicates assessment of the temperatures under which insect larvae have grown. The body may also be concealed in wrappings that delay fly access, or dumped at night when flies are usually inactive. Additionally, maggots may develop at different rates on perinatal remains, and on products of conception, than on adult bodies. This is because large maggot masses, which elevate temperatures, are less likely to form within smaller bodies. The difficulties inherent in this special case type are discussed, along with some solutions.

Effect of massing on larval growth rate

Estimation of minimum postmortem interval commonly relies on predicting the age of blowfly larvae based on their size and an estimate of the temperatures to which they have been exposed throughout their development. The majority of larval growth rate data have been developed using small larval masses in order to avoid excess heat generation. The current study collected growth rate data for larvae at different mass volumes, and assessed the temperature production of these masses, for two forensically important blow fly species, Chrysomya rufifacies and Calliphora vicina. The growth rate of larvae in a small mass, exposed to the higher temperatures equivalent to those experienced by large masses, was also assessed to determine if observed differences were due to the known temperature effects of maggot masses. The results showed that temperature production increased with increasing mass volume, with temperature increases of 11°C observed in the large Ch. rufifacies masses and increases of 5°C in the large C. vicina masses. Similarly, the growth rate of the larvae was affected by mass size. The larvae from small masses grown at the higher temperatures experienced by large masses displayed an initial delay in growth, but then grew at a similar rate to those larvae at a constant 23°C. Since these larvae from masses of equivalent sizes displayed similar patterns of growth rate, despite differing temperatures, and these growth rates differed from larger masses exposed to the same temperatures, it can be concluded that larval growth rate within a mass may be affected by additional factors other than temperature. Overall, this study highlights the importance of understanding the role of massing in larval development and provides initial developmental data for mass sizes of two forensically important blowfly species commonly encountered in Australian forensic casework.

Tracking Movement and Temperature Selection of Larvae of Two Forensically Important Blow Fly Species Within a “Maggot Mass”

The current study responds to the lack of understanding about the temperatures experienced by individual blow fly larvae within "maggot masses." The temperature selection of both aggregating (in a mass) and nonaggregating larvae was compared and their pattern of movement assessed. Infrared imaging determined the temperatures within a mass and in the vicinity of the constituent individual larvae, whose movements were tracked by dyeing their tissues red. Individual Chrysomya rufifacies larvae selected temperatures above 27°C, significantly higher than the temperature selected by Calliphora vicina larvae (24.5°C). However, this same difference was not seen within a mass, with both species selecting temperatures around 28°C. Larval movement in a mass was nonrandom, indicating that larvae actively select their position in a mass. Furthermore, larvae have a strong tendency to select the hottest part of a mass; therefore, maximum mass temperatures might provide a reliable proxy for the actual temperatures experienced by larvae.

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.

Thermogenesis in decomposing carcasses

It is of fundamental importance in forensic entomology that the factors controlling carcass temperatures during decomposition are thoroughly understood. The thermal environment to which fly larvae are exposed is the primary influence on their growth rate, and hence affects any estimate of minimum time since death using such specimens in homicide investigations. To date, much of the entomological research on maggot masses has focused on their elevation of carcass temperatures, with very little focus on the bacteria associated with larval activity. The aim of this study was to investigate the heat associated with decay and the types of bacteria present during the decomposition of a carcass, both in the presence and in the absence of maggots. Three treatments were imposed: fresh, frozen and maggot-infested, each consisting of five replicate pig carcasses. Temperature measurements and bacterial swabs were taken from the gastro-intestinal region of each pig and temperatures and bacterial communities compared between treatments. All carcasses reached average maximum temperatures above 32°C in a temperature controlled room set at 23°C. Treatment had no statistically significant effect on the temperatures recorded in each carcass but did significantly affect the community structure of the bacteria. However, bacterial community structure varied across time. This study suggests that bacterial metabolism plays a significant role in carcass thermogenesis, and that maggot masses, while contributing to localised heating within the carcass, may have less of a role in elevating carcass temperatures than previously assumed.