Forensic entomology was first documented in China in 1235 A.D. in the book entitled The Washing Away of Wrongs: Forensic Medicine in Thirteenth Century China (University of Michigan, Ann Arbor, MI). Sung Tzu, a “death investigator,” discovered the person responsible for a murder by the flies attracted to the victim’s blood on the assailant’s weapon.
The French scientists Bergeret, Brouadel, Yovanovitch, as well as Megnin introduced forensic entomology into Europe during the 19th century.
Forensic entomology reached the United States in 1898. Dr. Murray Motter examined the stages of decomposition and insect succession on buried human remains ranging in age from six months to 25 years.
Not until 1963 did we see forensic entomology revisited in the United States. Jerry Payne conducted extensive decomposition research that focused on the insects colonizing pig remains. Even today, his work is highly regarded for its level of detail regarding the insects colonizing carrion.
During the 1980’s, examining insects that colonize carrion in the context of forensic investigations exploded. The laboratories of Bernard Greenberg (University of Illinois at Chicago), Lamar Meek (Louisiana State University), and M. Lee Goff (University of Hawaii at Manoa) produced entomological studies in a forensic context.
Since 1999, more than 235 scientific articles containing the phrase “forensic entomology” have been published. A majority of these articles were written by United States scientists. Also, with the work of Gail Anderson (Simon Fraser University, Vancouver, Canada), John R. Wallace (Millersville University, Pennsylvania) and Richard W. Merritt (Michigan State University), forensic entomological studies have begun to address the relationship of aquatic organisms in criminal investigations.
Today, there are three books published on forensic entomology (Figure 1). Kenneth G.V. Smith (British Museum of Natural History) wrote the first text on forensic entomology in 1986, which is entitled A Manual of Forensic Entomology (Trustees of the British Museum, London, UK). This text is no longer in print, and although it is based on applications of forensic entomology in Europe, it contains interesting case studies, as well as a detailed description of the application of entomology as evidence in criminal investigations. E. Paul Catts and Neal Haskell edited the second text, Entomology & Death: A Procedural Guide (Joyce Print Shop, Clemson, SC), which was published in 1990. It is still available and is an excellent resource for investigators or others that have an interest in forensic entomology but do not have an entomology background. Jason H. Byrd and James L. Castner edited the most recent text, Forensic Entomology: The Utility of Arthropods in Legal Investigations (CRC Press, New York, NY), on forensic entomology, which was published in 2001. This text is more oriented to entomologists or other crime scene investigators.
POSTMORTEM INTERVAL (PMI): Insects and the associated larvae, especially flies and their maggots, are often collected from a corpse in order to determine the PMI. This calculation is accomplished primarily by understanding the relationship between the insect life cycle and past temperatures occurring at the body recovery site from death until recovery. Insects primarily are dependent on external sources of heat to develop. Typically, if it is hot, the insect will complete its life cycle in less time than when it is cooler.
ENTOMOTOXICOLOGY: Typically, blood, urine, or tissues undergo laboratory analysis to determine the presence of various toxins, as well as controlled and non-controlled substances. However, in cases where the body has gone undiscovered for a substantial period of time, these resources often cannot be directly recovered from the corpse because of the level of decomposition. However, it is now known that the insects, primarily maggots, present on remains can be recovered and examined for these substances. In fact, several drugs or chemicals can influence the growth and/or development of the maggots of fly species, thus influencing the determination of the post-mortem interval.
MOVEMENT OF THE REMAINS/PRIMARY V. SECONDARY CRIME SCENES: Insect species can be restricted to a given region or environment. Some insects that are present in a given environment will colonize human remains that are placed there. If the remains are then relocated to a new environment after initial insect colonization, it is possible that those insects present on the corpse will not match those present in the new environment. This finding would indicate that there is a primary (where the corpse was originally placed) and secondary crime scene (the location to where the corpse was moved).
ANTEMORTEM WOUNDS: Insect colonization patterns on a corpse have been well documented. Typically, insects will initially colonize or lay eggs around the moist regions particularly associated with the nose, ears, and mouth. Insects will also colonize any wounds that might have occurred prior to death (antemortem) or the anal and genital region if exposed. Colonization of antemortem wounds leads to variation in the decomposition process. Defensive wounds to the hands or arms are common examples of sites where abnormal colonization patterns have been observed; therefore, it is important for investigators to make observations of insect colonization sites prior to moving the body.
DNA: DNA collected from remains is one of the most common methods for identifying the victim, and in some cases, the assailant. Fly larvae or in certain situations, blood-feeding insects, can be collected and DNA from their gut contents can be extracted for identification (DNA fingerprinting) of its source.
ABUSE AND NEGLECT: Not all medico-legal cases within forensic entomology involve a deceased victim. In some cases, an individual might be neglected, and insects have taken advantage and colonize necrotic tissue, fecal material, or other decomposing matter present on the person. In these cases, it is important to collect and preserve (see below) representative specimens of these insects for examination by a forensic entomologist.
WILDLIFE AND DOMESTIC POACHING: State and federal laws protect many game animals and domestic animals. In some instances, animals are discovered poached. The same techniques used to collect insect evidence from a decomposing human corpse can also be used for decomposing wildlife or domestic animals.
There are many insect species that will colonize human remains. The species reviewed below are the common ones encountered.
BLOW FLIES: These insects are members of the insect order Diptera: family Calliphoridae. Blow flies, or bottle flies, are metallic in color and are usually the primary colonizers of human remains. These insects can be separated into two general groups. The blue bottle flies are metallic blue and are common during the cold periods of the year, while the green bottle flies are common during warmer periods. These insects are known to locate and deposit eggs on a human corpse in some cases minutes after death. Once the eggs hatch, resulting larvae (maggots) will feed on the soft tissue of the corpse. After a given period of time and growth, the maggots will migrate several feet away from the body to pupate. The pupae of these insects are brown and football-shaped. Pupae can be commonly found on the clothing of the deceased in an indoor setting or in the soil under and surrounding the corpse in a recovery site located outdoors.
FLESH FLIES: These insects are members of the insect order Diptera: family Sarcophagidae and are also colonizers of human remains. Many species are large gray flies with three black stripes on their backs, and their abdomen can be characterized in some cases by the posterior tip being orange or red. Their life cycle is different from blowflies in that they do not lay eggs but deposit live larvae. In other words, these insects give live birth and will lay maggots directly on the corpse.
CARRION BEETLES: These insects are in the insect order Coleoptera: family Silphidae. They are easily recognized from other beetles by their clubbed or knobbed antennae. Their elytra, or front wings, are shortened, which results in the last 2 or 3 segments of their abdomen being exposed when viewed from above. The larvae of these insects do not resemble the adults. The adults and larvae are known to feed on decomposing tissue and in some cases will prey on fly maggots.
ROVE BEETLES: These insects are in the order Coleoptera: family Staphylinidae. These beetles are long and slender with very short wings; therefore, most of the abdominal segments are exposed. The larvae do not resemble the adults. These insects are common throughout the decay process and will feed on a variety of resources. The first species to arrive are usually predaceous, feeding on fly eggs and maggots. Some species might be predators, while others will feed on fungi or carrion tissue.
SKIN BEETLES: These insects are in the insect order Coleoptera: family Dermestidae. These beetles commonly occur on human remains late in the decomposition process when most of the soft tissue has already been removed. The adults of the more common species are small (3/8 to 1/2 inch) and bullet-shaped. They can often be identified by their underside being frosted in appearance due to a covering of fine hair. The larvae (woolly bears) of these beetles do not resemble the adults and feed on the dry hair, skin, and cartilage of the corpse. They are also known to be cannibalistic. Therefore, adults should be stored separately from larvae.