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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.

Forensic entomology subfields

Urban forensic entomology

Urban forensic entomology typically concerns pests infestations in buildings, gardens, or other urban environments, and may be the basis of litigation between private parties and service providers such as landlords or exterminators. For instance, urban forensic entomology can be used to evaluate the efficiency of pest control techniques, ascertain the size of the infestation, and identify the responsible party in situations involing pest infestations in rental homes. Urban forensic entomology studies may also indicate the appropriateness of certain pesticide treatments and may also be used in stored products cases where it can help to determine chain of custody, when all points of possible infestation are examined in order to determine who is at fault. For example, urban forensic entomology can assist in determining responsability when stored goods, like grais or packaged foods, are contaminated with insects. It can also help identify the infestation origin. Moreover, environnemental management and public health depend heavily on urban forensic entomology. Researchers can track the transmission of disease carried by insects by examining insect populations in urban settings. Furthurmore, it can also guide coservation efforts by evaluating the environmental effects of urbanization on insect populations.

Stored-product forensic entomology

Stored-product forensic entomology is often used in litigation over insect infestation or contamination of commercially distributed foods. Insect infestations in stored goods, including grains, flour, and packaged meals, are the subject of this branch of forensic entomology, which also examines the legal ramifications of these findings. Stored-product forensic entomologists may be asked to identify the bug species involved, elvaluate the amount of the infestation, and pinpoint the infestation's source in a legal proceeding. In addition, they might offer expert testimony about the circumstances that gave rise to the infestation and suggest safeguards to stop it from happening again.

Forensic entomology on stored products not only helps with legal matters but also with food safety and quality assurance. Forensic entomologists work to guarantee that food products are safe for cosumption by identifying insect species and tracking their presence in stored goods. Additionally, this sector contributes to the general enhancement of food buisness practices by researching and developping novel techniques for pest management and product preservation.

Further information: Home stored product entomology

Medico-legal forensic entomology

Medicolegal forensic entomology involves the study of arthropods found at the scene of various incidents such as murder, suicide, rape, physical abuse and contraband trafficking. In murder investigations, forensic entomologists analyzes with which insects eggs appear, their location on the body and their development stage to determine the PMI and the location of death. The presence of specific insects species, which may exhibit endemism (occurring only in certain places), or have a well-defined phenology (active only at a certain season, or time of day), their presence in association with other evidence can provide crutial links to times and locations where other events may have occurred. This discipline also helps link victims, suspects and scenes together by identifying different insect species found in specific geographical locations.

Another area covered by medicolegal forensic entomology is entomotoxicology, a relatively new field that involves testimg entomological specimens found at a scene for drugs that may have played a role in the victim's death. The presence of drugs within the carcass can affect the growth and morphology of insects ingesting the toxinx, providing valuable evidence for forenisc investigations.However, relying solely on the physical development of insects affected by drugs for PMI estimation can lead to erronous interpretations.

Because it can show the location of injuries, entomology can also be useful in medicolegal issues. To give their larvae a liquid protein to feed, blow flies, for instance, lay their eggs close to wound sites or natural orfices, wich idicates where injuries on the body are located.

Myiasis

Myiasis, the infestation of living vertebrate aminals with dipteran larvae, is a phenomenon that may be noted in cases of abandonment or neglect. This conition occors when blow flies colonizing a human or animal in life, feeding on the organism's living tissues, injesting food, or liquid body sustances. In a forensic context, myasis can be confucing as it may indicate the time of neglect or injury, rather that the time of death, if the victim or remains were colonized when alive and prior to discovery. This highlights the importance of careful interpretation of entomologica; evidence in forensic investigation.

The role of insects in the decomposition processes

When it comes to the breakdown of organic materials, including human bodies, insects are essentials. Chemical emitted during decomposition attract necrophilic insects, or insects that feed on dead creatures. These insects hasten the decomposition process by aiding in the breakdown of bodily tissues. Among the first insects to reach a body, blow flies are regared as primary colonizers. Their oviposited eggs are laid in natural openings, wounds, or damp places, and decaying tissues are consumed by their maggot larvea. By feeding on the remnants, other insects like mites and beetles may also aid in the decomposition process.

Forenisc investigators can learn important details from insects' activites, including the length of time passed since death, the presence of medication or toxins in the body, and the movement or disturbance of the body following death.

Invertebrates types

Flies

Flies from the order Diptera are often insects found at a crime scene, because they are attracted to the chemicals released by decomposing bodies called volatile organic compounds (VOCs).  A dead body is a perfect environment for the ovoposition - to lay their eggs. The maggots will then have food to feed on. Different types of flies can be found on dead bodies the most significant include:

Beetles

Beetles (Order Coleoptera) are generally found in later stages of decomposition. They play a role in breaking down the remaining tissue and are important in the final stages of decomposition. In drier conditions, the beetles can be replaced by moth flies (Psychodidae). Their life cycle normally consists of four stages : eggs, larval, pupal, and adult. Each stage has unique eating behavior that chnages as the organism breacks down. In forensic investigations, the existence and developmental phases of insects can yield important data for understanding environmental circumstances, body movement, and postmortem interval (PMI) estimation. In forensic entomology, insects play a crucial function as indicators, helping to identify vital components of a death investigation due to their distinct ecological responsibilities and varied geographic distribution. Different types of beetles can be found on dead bodies the most significant include:

Insect succession

Insect succession, as utilized in forensic entomology, refers to the orderly progression of insect colonization and decomposition processes on a corpse over time. Their life cycle tipically consists of four stages : eggs, larval, pupal, and adult. Each stage has unique eating behavior that changes as the organism breacks down. In forensic investigations, the presence and developmental phases of insects can provide important data for understanding environmental circumstances, body movement, and postmortem interval (PMI) estimation. In forensic entomology, insects play a crucial role as indicators, helping to identify key components of a death investigation due to their distinct ecological responsibilities and varied geographic distribution. Given that different insect species inhabit a body in a certain order, understanding insect succession is essential for predection the postmortem interval (PMI). Typically, insect sucession occurs in the following stages:

1. Fresh stage: Marked by the arrival of necrophagous insects attracted to the body by chemicals, such as flesh flies and blowflies. These insects deposit their eggs (oviposit) on or near to the body, and the decaying tissues are the maggot's food source.
2. Bloated stage: The body starts to swell as a result of gas buildup during the breakdown process. During this phase, insects such as cheese skipper and coffin flies become more common.
3. Decay stage: In this stage, the insect community changes as the body goes through a more advanced state of decomposition. Predatory insects and mites increase in number, as do beetles, such as dermestid beetles and rove beetles.
4. Dry stage: The body dries up and the skeletal remains become visible during the last phases of decomposition. Scavenger insects and animals may be present on the remains, along with insects like ham beetles and hide beetles.

Postmortem interval estimation

A crucial component of forensic entomology is the calculation of the postmortem interval (PMI), which mostly depends on the observation of the insect activity on a corpse. Using the life stages of insects discovered on or near a body, forensic entomologists can reasonably determine how long it has been since a person died.

The pace of insect colonization and development is influenced by a number of variables, including as temperature, humidity, the presence of other living things and others. The accumulated degree hour (ADH) approch, which determines the total amount of heat energy generated by a body since death, is one of the models and methodologies used by forensic entomologists to estimate the PMI.

Even through PMI estimation based on insect evidence is typically accurate, it's crucial to take into account additional elements including body position, ambiant circumstances and insect behavior that may have an impact on insect activity.

Factors

Humidity

Both the decomposition and insect activity on a corpse are significantly influanced by humidity. Elevated humidity can hasten the decomposition process by fostering microbial proliferation, which facilitates the breakdown of tissues. Additionally the odors and gases produced by this microbial activity draw insects to the body. These smells are particularly attractive to insects like blowflies and flesh flies, which may quickly populate a body in humid conditions.

Low humidity, on the other hand, can impede the breakdown process. Mummification rather that breakdown may result from the body losing moisture more quickly in arid settings. Given that many insects need damp atmosphere to survive, this may discourage their activity. Nonetheless, some insects, like dermestid beetles, can survive in dry environments and can still be found on a body.

The existence of standing water next to a body can also affect the activity of insects. Aquatic insects, such as water beetles and some fly species, may be drawn to bodies near water sources. These insects can colonize the body and hasten its decomposition. Furthermore, because different insect species have distinct preference for habitats, the presence of water might influence the kinds of insects that inhabits the body.

All things considered, the rate and pattern of a corpse's decomposition and insect colonization are greatly influenced by its humidity. To estimate the postmortem period and reconstruct the circumstances around a death, forensic entomologists can benefit from an understanding of how humidity levels affect decomposition.

Sun exposure

"Because insects are cold-blooded animals, their rate of development is more or less dependent on ambient temperature." Bodies exposed to large amounts of sunlight will heat up, giving the insects a warmer area to develop, reducing their development time. An experiment conducted by Bernard Greenberg and John Charles Kunich with the use of rabbit carcasses to study accumulation of degree days found that with temperature ranging in the mid 70s to high 80s the amount of developmental time for maggots was significantly reduced.

In contrast, bodies found in shaded areas will be cooler, and insects will require longer growth periods. In addition, if temperatures reach extreme levels of cold, insects instinctively know to prolong their development time in order to hatch into a more accepting and viable climate in order to increase the chance of survival and reproduction.

Furthermore, insect activity and colonization patterns can also be influenced by the length and intensity of solar exposure. Because the increasing temperature speeds up their development, insects are more likely to be active and colonize a body more quickly in places exposed to direct and extended sunlight. In comparison to shaded locations, this may result in a quicker succession of insect life and disintegration stages. On the other hand, because of the lower temperatures, shaded areas might have slower rates of insect activity and decomposition, which would delay the processes of insect colonization and decomposition.

Air exposure

Air exposure can have a significant impact on insects and the determination of postmortem interval (PMI). Hanged bodies can be expected to show their own quantity and variety of flies. Also, the amount of time flies will stay on a hanged body will vary in comparison to one found on the ground. A hanged body is more exposed to air and thus will dry out faster, leaving less food source for the maggots.

The presence and behavior of insects on haging bodies can vary. As the body begins to decompose, a compilation of fluids will leak to the ground. This area is where most of the expected fauna can be found. Also, it is more likely that rove beetles and other non-flying insects will be found here instead of directly on the body. Fly maggots, initially deposited on the body, may also be found below.

modern techniques

Many new techniques have been developed and are used in order to more accurately gather evidence, or reevaluate old information. The use of these newly developed techniques and evaluations have become relevant in litigation and appeals. Forensic entomology not only uses arthropod biology, but it pulls from other sciences, introducing fields like chemistry and genetics, exploiting their inherent synergy through the use of DNA in forensic entomology. In order to improve the precision and dependability of insect-based evidence analysis, forensic entomologists nowadays use a variety of cutting-edge technologies, such as stable isotope analysis and DNA analysis. These methods have broadened the field of forensic entomology by making it possible to identify insect species more precisely, pinpoint their geographic origins, and draw important conclusions about the circumstances surrounding a death. Some of the most important contemporary forensic entomology techniques are examined in this section along with how they are applied to criminal investigations.

DNA analysis

Modern forensic entomology now relies heavily on DNA analysis as a fundamental tool for accurately identifying insect species and gaining important insights into their interactions with human remains. Using this method, DNA is extracted from insect specimens discovered at crime scenes and compared to databases containing known DNA sequences. Forensic entomologists can verify species identification, identify the existence of particular species linked to decomposition, and even establish a connection between insects and particular geographical areas through the examination of insect DNA.

The identification of insect stomach contents is one of the main uses of DNA analysis in forensic entomology. Investigators can ascertain the insect's most recent meal by sequencing the DNA contained in the gut of maggots or other insect larvae discovered on a body. When determining the postmortem interval (PMI) or locating possible sources of contamination or infection, this information might be extremely important.

The study of insect dispersal patterns and colonization behaviour has also been transformed by DNA research. Researchers can deduce patterns of travel and colonization by examining the genetic variety of insect populations. This can provide important insights into the origin of insect specimens found at crime scenes or the transportation of a body.

In general, DNA analysis has improved forensic entomology's accuracy and dependability significantly, allowing investigators to obtain previously unobtainable specific information from insect evidence.

Stable isotope analysis

A contemporary method that is being used more and more in forensic entomology to shed light on the ecology and life cycle of insects connected to human remains is stable isotope analysis. Using this technique, the stable isotopic composition of elements found in insect tissues, including carbon, nitrogen, hydrogen, and oxygen, is measured. The environment in which the insect developed, including its diet and place of origin, is reflected in these isotopes.

Stable isotope analysis provides information on the travel of the body or the insect itself, and can be used in forensic investigations to assist identify the geographic origin of insects found on a body. Furthermore, features of the insect's diet, such as whether it consumed organic matter or human remains, can be inferred by stable isotope analysis. This information can be vital to comprehending the insect's function in the decomposition process.

When using traditional methods to identify insect species or estimate age, this methodology has proven quite helpful. Stable isotope analysis contributes to more accurate and thorough forensic studies by improving the precision and depth of forensic entomological investigations by offering a distinct chemical signature that represents the insect's surroundings.