Forensic Entomology

Introduction
In so far as academic studies are concerned, the field of forensic entomology is relatively new in the West—but so, too, for that matter is the field of criminology. Forensic entomology is a subset of criminology in that it focuses on the study of insects and anthropods and what they reveal about the death of a victim. This highly specialized science takes the field of entomology and combines it with the field of forensics, bringing together two very different but very useful bodies of knowledge that, when they intersect, provide valuable insights that can help investigators solve murders. This paper will define and discuss forensic entomology, examine its history and how it has developed over the years, and describe how entomology has affected the field of forensics with a few examples to illustrate this point.
History
The history of forensic entomology begins, as far as historical records show, in China in the 13th century. This is where Sung Tzu, who wrote many other works, composed two in particular that touched on forensic entomology. The first was Collected Cases of Injustice Rectified and the second was Washing Away of Wrongs. The latter dealt with identifying the causes of death and how to examine the corpse for information. The former told the story of the peasant who slew his neighbor with a sickle and was identified by the murder weapon, which attracted flies—drawn by the traces of blood left on the blade, unseen by the human eye (Rivers & Dahlem, 2014). The insects helped the authorities determine the murder weapon and the identity of the man whose weapon it was. This is the earliest known example of forensic entomology.
Other examples followed. There was Redi in 17th century Italy who proved that maggots are not spontaneously generated in the rotting meat but actually grow from flies (Rivers & Dahlem, 2014). Redi’s proof prompted more investigation into the role of insects in the decomposition of flesh. This was followed by Bergeret in France in the 19th century who applied the science of forensic entomology to an actual case for the first time in modern history. Bergeret used the evidence of larvae and pupae to conjecture about the “mummified remains of a newborn baby” (Rivers & Dahlem, 2014, p. 18) and thus made history in the West with what is now known as the first instance of forensic entomology as it is used today.
In the 20th century, the field of entomology itself began to develop even more, and as the world proceeded to go to war there was ample opportunity to apply developments in the field of entomology to the burgeoning field of forensics. Pest control was a major focus during both World War I and World War II, and by 1922 Karl Meixner had observed that the decomposition of bodies infested with maggots proceeded more quickly when the cadaver was that of a child as opposed to that of an elderly person (Rivers & Dahlem, 2014). Hermann Merkel provided insights into how wounds to a body could alter the rate of decomposition by facilitating access to insects. Josef Holzer investigated the effect of aquatic insects on submerged bodies and how certain species impacted the skin in different ways and when caddisflies lay larvae, which allowed him to guess that a particular body had been underwater for seven days, based on the fact that he found caddisfly larvae on the cadaver.
These were just a few of the examples of what investigators were doing, merging entomology with forensics. By the latter half of the 20th century, their work would begin to be studied with real earnest by professionals in the field of criminal justice, as forensics become more and more in demand and the need to know more about the possible cause and time of death put forensic entomologists on the map.
Development of Forensic Entomology
By the 1990s, three forms of forensic entomology had developed. These were urban forensic entomology, stored-product forensic entomology, and medicolegal forensic entomology—or better known today as the most commonly known form of forensic entomology, the form that “deals with anthropod involvement in events surrounding felonies, usually violent crimes such as murder, suicide, and rape” as well as “other violations such as physical abuse and contraband trafficking” (Catts & Goff, 1992, p. 253). Urban forensic entomology focused less sensational issues—such as the lawsuits surrounding pests and anthropods in residences or the wrongful use of pesticides. Stored-product forensic entomology focused on commercial products that had been infested—such as maggots in candy bars or spiders in tissue paper (Catts & Goff, 1992). While each of these forms of forensic entomology have their application in modern day law and criminal justice, the form of forensic entomology that is most popularly applied is the third form already described here and also more accurately known as mediocriminal forensic entomology.
It is this latter form that has the most utility in crime scene investigations. How is it advantageous to today’s crime scene investigators? As Joseph, Mathew, Sathyan and Vargheese (2011) note, “by studying the insect population and the developing larval stages, forensic scientists can estimate the postmortem index, any change in position of the corpse as well as the cause of death” (p. 89). In other words, forensic entomology helps investigators better understand what happened, where it happened, when it happened and how it happened, when they are trying to piece the evidence together and solve a murder, rape, trafficking incident, abuse case, or some other form of crime in which insects and anthropods can help to tell the story.
Knowing about how insects and anthropods feed and nest is crucial, however—which is why the field of entomology is necessary. Forensics would not be the same had entomologists not first began undertaking the study of insects and anthropods in earnest in the 19th and 20th centuries. It was their studies that helped others better understand the crimes of the modern era.
The development of entomology is crucial to understanding crime scene evidence and especially gauging the length of time a cadaver has been a specific place. Without forensic entomology investigators would be handicapped—only able to use medical instruments and measures—such as examining the extent to which rigor mortis has set in, an approach only helpful for pinpointing the time of death a day or two after it has occurred. For cadavers discovered days or weeks after death, medical measures are useless—but scientists who understand nature and in particularly the role that insects and anthropods play in the decomposition process can help stitch together the clues: “by calculating the age of immature insect stages feeding on a corpse and analyzing the necrophagous species present, postmortem intervals from the first day to several weeks can be estimated”—a much more robust approach to understanding the evidence than applying mere medical science (Amendt, Krettek & Zehner, 2004, p. 51).
How Entomology Has Affected the Field of Forensics
Greenberg (1985) states that when examining a corpse an understanding of entomology with respect to species of flies is of particular use, as this knowledge can be used to determine the nature of the case more accurately. For instance, while there are several varieties of flies that will can be found at a crime scene regardless of whether the victim is alive or dead, there are other species that will only be found infesting corpses: “most important for estimating post-mortem interval are the carrion or sarcosaprophagous flies, with calliphorids first and sarcophagids second” (Greenberg, 1985, p. 25). Had investigators no access to this information or no way of distinguishing one species of fly from another, they would lack the capacity to obtain “clues not only to time or season but also to place (e.g. rural or urban, endophily or exophily, and even geography)” (Greenberg, 1985, p. 25). Information about species of insects and anthropods, however, allowed the field of forensics to blossom into a much more rigorous and scientific study, using the natural world to obtain clues needed to understand a crime.
From flies to beetles to mites, moths, wasps, ants and bees, entomologists were able to bring to forensics a whole host of knowledge regarding the insect and anthropod world that could be applied to the study of crime scene to better understand it. Not only this knowledge but also knowledge of the elements became helpful—such as what insects appear at certain moisture levels, what anthropods can be found in water and what they do to flesh after a certain period of time; how insects react to bodies exposed to the sun, to air; how geography and weather play a part in determining the behavior of insects with regard to a corpse—all of this information has become important in the field of forensics now that it is known that entomologists bring a perspective on the natural world that can be wholly useful to investigators of a crime scene (Greenberg & Kunich, 2002).
For example, entomologists know that the first species of fly to respond to a cadaver’s presence is the blow fly, because it can smell the rotting corpse from ten miles distance (Byrd & Castner, 2001). Distinguishing this fly from others and knowing the pace at which it can begin to feed and lay larvae help investigators pinpoint the postmortem interval with more certainty.
Technology can also be used by entomologists to see things that the human eye cannot see. Scanning electron microscopy, potassium permanganate staining, mitochondrial DNA, and gene expression studies have all been techniques used by forensic entomologists to obtain information about a cadaver that could help investigators describe the scenario more accurately, effectively and efficiently.
Examples
Benecke (1998) provides half a dozen cases of how forensic entomology has been applied in crime scene investigation. One example given is of a case of a deceased heroin user, overdosed in a flat—but his body had been carried outside at some point, as evidenced by the blowfly eggs found on the cadaver. Another example, this one from Thailand, where 30 cadavers were the subject of forensic entomology studies from 2000 to 2006, with death scenes determined by the fly specimens identified on each cadaver: death scenes ranged from urban indoor and outdoor settings to suburban areas to forests (Sukontason et al., 2007).
Forensic entomology has even been helpful in determining the nature of child and elderly abuse as “wounds of living persons are a potential target for the same flies that live, or feed early on corpses” (Benecke, Josephi & Zweihoff, 2004, p. 195). In such cases, forensic entomologists can provide valuable information that can be admitted at trial to convict abusers. Malpractice in the case of elder abuse and child abuse by caretakers has received attention from forensic entomologists, whose work has been found to be extremely constructive in helping to determine timelines of abuse.
In Hawaii, forensic entomology was used in three different cases to determine the time of death from as soon as eight days postmortem to an astonishing 53 days postmortem (Goff & Odom, 1987). Had entomology not merged with forensic science, no such time of death pinpointing would be possible. Three cases in Italy proved the extent to which forensic entomology was applicable as well, with postmortem interval determined in each of the three cases “based on comparison of data from autopsy reports (rate of decay), local environmental conditions (temperature, humidity, rainfall) and development times for the immature stages of each species of local arthropod and succession patterns” (Introna, Campobasso & Di Fazio, 1998, p. 210). In each case, however, it was the evidence supplied by the forensic entomologist that led to a conclusive determination of the postmortem interval, with the first case having a postmortem interval of one week, based on the finding of adult Saprinu aeneus and mature larvae of Chrysomya albiceps. In the second case involving a corpse charred beyond recognition, the larvae of Sarcophaga haemorrhoidalis and Protophormia Terraenovae were found in varying stages of development, indicated a postmortem interval of 3 or 4 days. The third case involved two more burned corpses, on which were found Calliphora vicina, indicating a postmortem interval of a day and half to two days. Without these measures, the postmortem interval would have been virtually unknowable to investigators (Introna et al., 1998).
These examples show clearly how the field of entomology has helped to advance the field of forensics by applying the laws of nature and the behaviors of insects and anthropods in the natural world to crime scene investigations so that a more comprehensive understanding of the evidence can be obtained. Just like the authorities of a village in ancient China did in the 13th century when they examined the scythes of the local peasants and found the flies attracted to one in particular, today’s investigators can turn to forensic entomologists to obtain a more robust understanding of postmortem interval, movement of the body, and other explanations for the evidence that can be used to piece together what happened, when and where.
Conclusion
In conclusion, the field of forensics has benefitted substantially from the field of entomology—mainly because entomologists have obtained information about the natural world that is useful in understanding what happens to a body after it dies. The insects and anthropods of the world have unique behaviors, with each species having its own approach to death, allowing those who understand these approaches to determine with a high degree of certainty the nature of death, the time of death, the place of death, and so on. Entomology has thus merged with the field of forensics out of necessity—because it brings so much utility and insight for investigators. Coupling the two makes sense today, just as it did nearly a thousand years ago in ancient China when the first historical record of forensic entomology was described in writing. Since that time, more and more attention has been paid to the natural world and to the behavior of insects and anthropods in particular. And since these creatures play a substantial role in the process of decomposition, they share in the story that crime scene investigators seek to retell in their own pursuit of justice.

References
Amendt, J., Krettek, R., & Zehner, R. (2004). Forensic entomology. 
Naturwissenschaften, 91(2), 51-65.
Benecke, M. (1998). Six forensic entomology cases: description and commentary. 
Journal of Forensic Science, 43(4), 797-805.
Benecke, M., Josephi, E., & Zweihoff, R. (2004). Neglect of the elderly: forensic
entomology cases and considerations. Forensic Science International, 146, S195-S199.
Byrd, J. H., & Castner, J. (2001). Forensic Entomology: The Utility of Arthropods in
Legal Investigations. Boca Raton, FL: CRC Press.
Catts, E. P., & Goff, M. L. (1992). Forensic entomology in criminal
investigations. Annual Review of Entomology, 37(1), 253-272.
Goff, M. L., & Odom, C. B. (1987). Forensic entomology in the Hawaiian Islands. Three
case studies. The American Journal of Forensic Medicine and Pathology, 8(1), 45-50.
Greenberg, B. (1985). Forensic entomology: case studies. American Entomologist, 31(4),
25-28.
Greenberg, B., & Kunich, J. (2002). Entomology and the Law. United Kingdom:
Cambridge University Press.
Introna, F., Campobasso, C. P., & Di Fazio, A. (1998). Three case studies in forensic
entomology from southern Italy. Journal of Forensic Science, 43(1), 210-214.
Joseph, I., Mathew, D. G., Sathyan, P., & Vargheese, G. (2011). The use of insects in
forensic investigations: An overview on the scope of forensic entomology. Journal of Forensic Dental Sciences, 3(2), 89.
Meixner, K. (1922). Morgue destruction by fly maggots, Z. Medical Officer , 35 , 407-
413.
Rivers, D. & Dahlem, G. (2014). The science of forensic entomology. NJ: Wiley.
Sukontason, K., Narongchai, P., Kanchai, C., Vichairat, K., Sribanditmongkol, P.,
Bhoopat, T., ... & Vongvivach, S. (2007). Forensic entomology cases in Thailand: a review of cases from 2000 to 2006. Parasitology Research, 101(5), 1417.