Carrion insects are insects associated with decomposing remains. The processes of decomposition begin within a few minutes of death. [1] Decomposing remains offer a temporary, changing site of concentrated resources which are exploited by a wide range of organisms, of which arthropods are often the first to arrive and the predominant exploitive group. However, not all arthropods found on or near decomposing remains will have an active role in the decay process. [2]
Carrion insects are commonly described based on their ecological role. [2] [3] Four commonly described roles are:
Necrophagous species are insects/arthropods that feed directly on remains, or the fluids released from remains during the decomposition process. [2] [3] This ecological classification includes many species of the order Diptera (true flies) from the families Calliphoridae (blowflies) and Sarcophagidae (flesh flies), and some species of the order Coleoptera (beetles). Although specific arthropod species present at remains will vary by geographic location, some examples of common blowflies are Calliphora vicina , Phormia regina , Protophormia terraenovae and Lucilia sericata
Necrophagous blowfly species are often the first to arrive and colonize at a site of decomposing remains. [2] These species develop from eggs laid directly on the carcass and complete their life cycle on or near the remains. Because of this, necrophagous species are considered to be the most important for post-mortem interval estimations. [4] [5] The initial colonizers of greatest importance are those of the family Calliphoridae, Sarcophagidae and Muscidae (house flies), as these are typically the first insects to lay eggs at remains. [5]
The fresh stage of decomposition is characterized by the arrival of necrophagous blowflies and flesh flies. These blowflies are also strongly attracted during the bloat stage of decomposition. [2] Many Dipterans, especially their larval forms, are involved in removal of material from the carcass, though not in an appreciable amount. [6] Necrophagous species of Coleoptera are most strongly attracted during the active stage of decomposition. [2]
This role includes those insects which feed on, or act as parasites of, necrophagous species. These insects do not feed directly on the decomposing remains or its fluids, but are considered to be the second most forensically important ecological role. [3] [7] Predators of necrophagous insects include species from the Coleoptera families Silphidae (carrion beetles) and Staphylinidae (rove beetles). [3] Parasites may include species of parasitic wasps, from the order Hymenoptera (family Braconidae).
Some species of blowflies may begin their larval development in the necrophagous role, feeding directly on remains, but become predaceous during later larval stages. These species are listed as being schizophagous, and are included in the predators and parasites ecological role. [3]
The majority of beetles present at remains are there as predators of blowfly larvae, and are not directly concerned with the removal of carcass materials. [6] Predaceous beetles may arrive at a site of remains as early as the bloat stage of decomposition, when there is a strong attraction of their necrophagous prey. Some of these species may also remain during active decay. During the advanced stage of decay there is an increase in those insects which are predaceous and/or parasitic on necrophagous beetles. [2]
Omnivorous species feed on both the decomposing remains as well as other carrion associated insects, usually necrophagous species. [2] [3] Large numbers of omnivorous insects can slow the rate at which carcass materials are removed by depleting the number of necrophagous larvae. [8] This category includes species of ants, wasps, and some species of carrion beetles. [2]
Adventive species may or may not play a significant role in the decomposition of remains. Arthropods in this ecological role are not necessarily attracted to decaying remains, but use it as an extension of their natural habitats. Adventive species originate within the vegetation and soils surrounding decomposing remains. These insects may visit remains from time to time, or use them for concealment, [9] but their presence can only be accounted for by chance. [2] They may also become predators of necrophagous species found at remains. [9] Adventive species include springtails, centipedes and spiders. [3]
The diagram below shows the relationship between each ecological role and a site of decaying remains.
The ecological roles described above can further be condensed into two broad, general classifications: [10]
This classification consists of necrobiont insects which use decaying remains as a permanent environment necessary for their life and development. Necrobiont insects includes necrophagous and entomophagous trophic specializations, [10] or necrophagous, predaceous/parasitic and omnivorous species.
Some insects or arthropods visit sites of carrion, but do not colonize them. [5] This classification consists of those insects for which decomposing remains are not a permanent feature for development. [10] The adventive trophic specialization falls into this category.
Each group or species of insect will be attracted to decomposing remains at different stages of decomposition, as changes within the remains result in the availability of different resources. The predictable order in which the above described insect groups are attracted to and observed on remains is referred to as a succession pattern, and can be used in forensic investigations to estimate the post-mortem interval (PMI) or time since death. [11] This method of PMI estimation is most useful in the later stages of decomposition. [12]
A second method of PMI determination, in early stages of decomposition, by insect evidence utilizes the development rate of colonizing arthropods. This method is usually applied to necrophagous blowflies, as they are often the first to colonize and are associated with remains for the longest period. Development rates are only useful in forensic investigations until the first new generation has completed development and left the remains. [2]
Forensic entomology is a field of forensic science that uses insects found on corpses to help solve criminal cases. This includes the study of insect types commonly associated with cadavers, their respective life cycles, their ecological presences in a given environment, as well as the changes in insect assemblage with the progression of decomposition. Insect succession patterns are identified based on the time a given species of insect spends in a given developmental stage, and how many generations have been produced since the insects introduction to a given food source. Insect development alongside environmental data such as temperature and vapor density, can be used to estimate the time since death, due to the fact that flying insects are attracted to a body immediately after death, determine any possible movement of the body after death, and the determination of antemortem trauma. The identification of postmortem interval to aid in death investigations is the primary scope of this scientific field. However, forensic entomology is not limited to homicides, it has also been used in cases of neglect and abuse, in toxicology contexts to detect the presence of drugs, and in dry shelf food contamination incidents. Equally, insect assemblages present on a body, can be used to approximate a given location, as certain insects may be unique to certain areas. Therefore, forensic entomology can be divided into three subfields: urban, stored-product and medico-legal/medico-criminal entomology.
Silphidae is a family of beetles that are known commonly as large carrion beetles, carrion beetles or burying beetles. There are two subfamilies: Silphinae and Nicrophorinae. Members of Nicrophorinae are sometimes known as burying beetles or sexton beetles. The number of species is relatively small, at around two hundred. They are more diverse in the temperate region although a few tropical endemics are known. Both subfamilies feed on decaying organic matter such as dead animals. The subfamilies differ in which uses parental care and which types of carcasses they prefer. Silphidae are considered to be of importance to forensic entomologists because when they are found on a decaying body they are used to help estimate a post-mortem interval.
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Animals, such as earthworms, also help decompose the organic materials. Organisms that do this are known as decomposers or detritivores. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word taphos, meaning tomb. Decomposition can also be a gradual process for organisms that have extended periods of dormancy.
Histeridae is a family of beetles commonly known as clown beetles or hister beetles. This very diverse group of beetles contains 3,900 species found worldwide. They can be easily identified by their shortened elytra that leaves two of the seven tergites exposed, and their geniculate (elbowed) antennae with clubbed ends. These predatory feeders are most active at night and will fake death if they feel threatened. This family of beetles will occupy almost any kind of niche throughout the world. Hister beetles have proved useful during forensic investigations to help in time of death estimation. Also, certain species are used in the control of livestock pests that infest dung and to control houseflies. Because they are predacious and will even eat other hister beetles, they must be isolated when collected.
Trogidae, sometimes called hide beetles, is a family of beetles with a distinctive warty or bumpy appearance. Found worldwide, the family includes about 300 species contained in four or five genera.
Cleridae are a family of beetles of the superfamily Cleroidea. They are commonly known as checkered beetles. The family Cleridae has a worldwide distribution, and a variety of habitats and feeding preferences.
Calliphora vomitoria, known as the blue bottle fly, orange-bearded blue bottle, or bottlebee, is a species of blow fly, a species in the family Calliphoridae. Calliphora vomitoria is the type species of the genus Calliphora. It is common throughout many continents including Europe, Americas, and Africa. They are fairly large flies, nearly twice the size of the housefly, with a metallic blue abdomen and long orange setae on the gena.
Forensic entomological decomposition is how insects decompose and what that means for timing and information in criminal investigations. Medicolegal entomology is a branch of forensic entomology that applies the study of insects to criminal investigations, and is commonly used in death investigations for estimating the post-mortem interval (PMI). One method of obtaining this estimate uses the time and pattern of arthropod colonization. This method will provide an estimation of the period of insect activity, which may or may not correlate exactly with the time of death. While insect successional data may not provide as accurate an estimate during the early stages of decomposition as developmental data, it is applicable for later decompositional stages and can be accurate for periods up to a few years.
Phormia regina, the black blow fly, belongs to the blow fly family Calliphoridae and was first described by Johann Wilhelm Meigen.
Chrysomya megacephala, more commonly known as the oriental latrine fly or oriental blue fly, is a member of the family Calliphoridae (blowflies). It is a warm-weather fly with a greenish-blue metallic box-like body. The fly infests corpses soon after death, making it important to forensic science. This fly is implicated in some public health issues; it can be the cause of myiasis, and also infects fish and livestock.
Sarcophaga bullata, or the grey flesh fly, is a species of fly belonging to the family Sarcophagidae. It varies in size from small to large, 8 to 17 millimeters in length and is very similar in appearance and behavior to a closely related species, Sarcophaga haemorrhoidalis. S. bullata is a common scavenger species in the Eastern United States, but is found throughout the Nearctic region. Identification down to the species level in the family Sarcophagidae is notably difficult and relies primarily on the male genitalia. Though limited information is available regarding S. bullata, it has gained increasing recognition in the field of forensic entomology as a forensically relevant fly species, as it may be among the first species to colonize human remains. In these instances, recovered maggots may be analyzed for post-mortem interval (PMI) estimations, which may be used as evidence in courts of law. Current studies regarding S. bullata have revealed a maternal effect operating in these flies that prevents pupal diapause under certain environmental conditions, which is an important factor to be considered during forensic analyses.
Cynomya cadaverina, also known as the shiny blue bottle fly, is a member of the family Calliphoridae, which includes blow flies as well as bottle flies. In recent years, this family has become a forensically important facet in many medicocriminal investigations in the growing field of forensic entomology. C. cadaverina is specifically important in determining a post-mortem interval, as well as other important factors.
Lucilia coeruleiviridis, formerly Phaenecia coeruleiviridis, is commonly known as a green bottle fly, because of its metallic blue-green thorax and abdomen. L. coeruleiviridis was first discovered by French entomologist Pierre-Justin-Marie Macquart in 1855. It belongs to the family Calliphoridae and is one of many forensically important Diptera, as it is often found on decaying substances. L. coeruleiviridis is one of the most ubiquitous blow fly species in the southeastern United States, particularly in the spring and fall months.
Calliphora latifrons is a species of blue bottle fly.
Creophilus maxillosus, the hairy rove beetle, is a species of rove beetle.
Oiceoptoma noveboracense is a member of the family Silphidae, or carrion beetles, which feed on decaying organic matter such as dead animals. Its common name is the margined carrion beetle, from the orange-red margins on the pronotum, which are helpful when identifying this species. The larva is typically light brown to red and also has vertical ridges on its thorax like the adult. This diurnal beetle can be found mainly in the spring into the fall, and it has a strong preference towards a deciduous forest habitat. The primary forensic importance of this beetle is its ability to use the succession of insect fauna to provide confirmation of postmortem intervals.
Necrophages are organisms that obtain nutrients by consuming decomposing dead animal biomass, such as the muscle and soft tissue of carcasses and corpses. The term derives from Greek nekros, meaning 'dead', and phagein, meaning 'to eat.' Mainly, necrophages are species within the phylum Arthropoda; however, other animals, such as gastropods and Accipitrimorphae birds have been noted to engage in necrophagy.
The necrobiome has been defined as the community of species associated with decaying corpse remains. The process of decomposition is complex. Microbes decompose cadavers, but other organisms including fungi, nematodes, insects, and larger scavenger animals also contribute. Once the immune system is no longer active, microbes colonizing the intestines and lungs decompose their respective tissues and then travel throughout the body via the blood and lymphatic systems to break down other tissue and bone. During this process, gases are released as a by-product and accumulate, causing bloating. Eventually, the gases seep through the body's wounds and natural openings, providing a way for some microbes to exit from the inside of the cadaver and inhabit the outside. The microbial communities colonizing the internal organs of a cadaver are referred to as the thanatomicrobiome. The region outside of the cadaver that is exposed to the external environment is referred to as the epinecrotic portion of the necrobiome, and is especially important when determining the time and location of death for an individual. Different microbes play specific roles during each stage of the decomposition process. The microbes that will colonize the cadaver and the rate of their activity are determined by the cadaver itself and the cadaver's surrounding environmental conditions.
Decomposition is the process in which the organs and complex molecules of animal and human bodies break down into simple organic matter over time. In vertebrates, five stages of decomposition are typically recognized: fresh, bloat, active decay, advanced decay, and dry/skeletonized. Knowing the different stages of decomposition can help investigators in determining the post-mortem interval (PMI). The rate of decomposition of human remains can vary due to environmental factors and other factors. Environmental factors include temperature, burning, humidity, and the availability of oxygen. Other factors include body size, clothing, and the cause of death.
Necrodes littoralis, also known as the short sexton beetle, is a species of carrion beetle of the genus Necrodes, found in countries across Europe. As a carrion beetle, it feeds on decaying vertebrate remains and maggots. This species' feeding behaviors make it an important asset to forensic entomology.