Forensic Entomology

Forensic entomology is the application and study of insect and other arthropod biology to criminal matters. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. Forensic entomology can be divided into three subfields: urban, stored-product, and medico-legal/medico-criminal entomology.

HISTORY

Historically, there have been several accounts of applications for, and experimentation with, forensic entomology. The concept of forensic entomology dates back to at least the 14th century. However, only in the last 30 years has forensic entomology been systematically explored as a feasible source for evidence in criminal investigations. Through their own experiments and interest in arthropods and death, Song Ci, Francesco Redi, Bergeret d’Arbois, Jean Pierre Megnin, and the German doctor Hermann Reinhard have helped to lay the foundations for today's modern forensic entomology.

Song Ci

Song Ci (also known as Sung Tz’u) was a Judicial Intendant who lived in China in the late 13th century. In 1247 AD Song Ci wrote a book entitled Washing Away of Wrongs as a handbook for coroners. In this book, Song Ci depicts several cases in which he took notes on how a person died, and elaborates on probable causes. He goes into detail on how to examine a corpse both before and after burial. He also explains the process of how to determine a probable cause of death. The purpose of this book was to be used as a guide for other investigators so they could assess the scene of the crime effectively. His level of detail in explaining what he observed in all his cases laid down the fundamentals for modern forensic entomologists and is the first recorded account in history of someone using forensic entomology for judicial means. This book was immensely popular and represented the first time that the general public became aware that insects could be used in criminal investigations.

Francesco Redi

In 1668, Italian physician Francesco Redi disproved the theory of spontaneous generation. The accepted theory of Redi's day claimed that maggots developed spontaneously from rotting meat. In an experiment, he used samples of rotting meat that were either fully exposed to the air, partially exposed to the air, or not exposed to air at all. Redi showed that both fully and partially exposed rotting meat developed fly maggots, whereas rotting meat that was not exposed to air did not develop maggots. This discovery completely changed the way people viewed the decomposition of organisms and prompted further investigations into insect life cycles and into entomology in general.

Bergeret d’Arbois

Dr. Louis Francois Etienne Bergeret (1814–1893) was a French hospital physician and was the first to apply forensic entomology to a case. In a case report published in 1855, he stated a general life cycle for insects and made many assumptions about their mating habits. Nevertheless, these assumptions led him to the first application of forensic entomology in an estimation of post-mortem interval (PMI). His report used forensic entomology as a tool to prove his hypothesis on how and when the person had died.

Hermann Reinhard

The first systematic study in forensic entomology was conducted in 1881, by Hermann Reinhard, a German medical doctor who played a vital role in the history of forensic entomology. He exhumed many bodies and demonstrated that the development of many different types of insect species could be tied to buried bodies. Reinhard conducted his first study in East Germany and collected many Phorid flies from this initial study. He also concluded that the development of only some of the insects living with corpses underground were associated with them, since there were 15-year-old beetles who had little direct contact with them. Reinhard's works and studies were used extensively in further forensic entomology studies.

Jean Pierre Megnin

Jean Pierre Mégnin (1828–1905), an army veterinarian, published many articles and books on various subjects including the books Faune des Tombeaux and La Faune des Cadavres, which are considered to be among the most important forensic entomology books in history. In his second book, he did revolutionary work on the theory of predictable waves, or successions, of insects onto corpses. By counting numbers of live and dead mites that developed every 15 days and comparing this with his initial count on the infant, he was able to estimate how long that infant was dead. In this book he asserted that exposed corpses were subject to eight successional waves, whereas buried corpses were only subject to two waves. Mégnin made many great discoveries that helped shed new light on many of the general characteristics of decaying flora and fauna. Mégnin's work and study of the larval and adult forms of insect families found in cadavers sparked the interest of future entomologists and encouraged more research in the link between arthropods and the deceased, and thereby helped to establish the scientific discipline of forensic entomology.

FORENSIC ENTOMOLOGY SUBFIELDS

Urban forensic entomology

Urban forensic entomology typically concerns pests infestations in buildings’ gardens or that may be the basis of litigation between private parties and service providers such as landlords or exterminators. 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.

Stored-product forensic entomology

Stored-product forensic entomology is often used in litigation over insect infestation or contamination of commercially distributed foods.

Medicolegal forensic entomology

Medicolegal forensic entomology covers evidence gathered through arthropod studies at the scenes of murder, suicide, rape, physical abuse, and contraband trafficking. In murder investigations, it deals with which insects’ eggs appear, their location on the body, and in what order they appear. This can be helpful in determining a post-mortem interval (PMI) and location of a death in question. Since many insects exhibit a degree of 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 demonstrate potential links to times and locations where other events may have occurred). Another area covered by medicolegal forensic entomology is the relatively new field of entomotoxicology. This particular branch involves the utilization of entomological specimens found at a scene in order to test for different drugs that may have possibly played a role in the death of the victim.

INSECT TYPES

There are many different types of insect studied in forensic entomology. The insects listed below are mostly necrophagous (corpse-eating) and are particularly relevant to medicolegal entomological investigations. This is not a full list, as there are many variations due to climate. The order in which insects feed on a corpse is known as “faunal succession.”

Flies

Flies (order diptera) are often first on the scene. They prefer a moist corpse for their offspring (maggots) to feed on. The most significant types of fly include:

Blowflies – Family Calliphoridae. Flies in this family are often metallic in appearance and between 10 to 12 mm in length. In addition to the name “blowfly,” some members of this family are known as glue bottle fly, cluster fly, greenbottles, or black blowfly. A characteristic of the blowfly is its 3-segmented antennae. Hatching from an egg to the first larval stage takes from eight hours to one day. Larvae have three stages of development (called instars). Each stage is separated by a molting event. Worldwide, there are 1,100 known species of blowflies, with 228 species in the Neotropics, and a large number of species in Africa and Southern Europe.
The most common area to find Calliphoridae species are in the countries of India, Japan, Central America, and in the southern United States. The typical habitat for blowflies are temperate to tropical areas that provide a layer of loose, damp soil and litter where larvae may thrive and pupate. The forensic importance of this fly is that it is the first insect to come in contact with carrion, because they have the ability to smell death (decomposing flesh) from up to 10 miles (16 km) away.

Flesh flies – Family Sarcophagidae. Most flesh flies breed in carrion, dung, or decaying material, but a few species lay their eggs in the open wounds of mammals; hence, their common name. Characteristics of the flesh-fly is its 3-segmented antennae. They are medium-sized flies with black and gray longitudinal stripes on the thorax and checkering on the abdomen. Flesh-flies, being ...