Author: Bryan Lin
Editors: Junyu Zheng and Sophia Chen
Artist: Kevin Lin
Although many view insects as repulsive and bothersome, they are quite valuable, especially in investigations. Forensic Entomology, in particular, is the study of insects for use in criminal cases and has yielded promising results in determining crucial aspects of criminal cases. Studies show that entomological data collected from the insects present on the carrion–a dead body–provide more accurate estimations of the time of death within 24 hours compared to medical examiners. But how does forensic entomology work exactly?
There are two distinct methods Forensic entomologists use to determine the time of death depending on how long the body has been dead. For bodies presumed to have been dead for months, entomologists look at the successional waves of insects found on the carrion. As the body begins the process of autolysis, a volatile molecule known as apeneumones is released. Insects of the Diptera (fly) and Coleoptera (beetle) genera are among the first to be attracted to and feed on the body. At this early stage, many insects are not interested in the body, though some, like the piophilidae, show up during later stages. Numerous insects that appear may not be specifically drawn to consume the body itself, but rather the insects that are attracted to the decaying flesh. As the carrion reaches its 90-day mark, the Diptera larvae have all but hatched and left, leaving byproducts of decay. Through analyzing the succession of insect species that are found on the carrion, as well as the traces of past insects that had fed on the carrion, entomologists can accurately estimate a window of the timeframe of death.
In contrast, the method used to calculate the time of death within a shorter window, spanning a few days up to a week, is known as maggot development. This approach looks at the age of the maggots of blowflies, which are usually the first insects to arrive at the dead body, found within the carrion. This method is reliable as the lifecycle of the maggots is very predictable, starting as larvae before molting into their second and third instar stage. When the larva finally reaches its third instar stage, it will find a safe place to pupate, turning into a blowfly. Upon examining the oldest stage of insect found on the carrion and considering the temperature of the environment where the body was located, entomologists can estimate the day or range of days when the initial blowfly laid its eggs on the corpse. This estimation can then determine the day or range of days when the person passed away. For instance, if the oldest insects are 7 days old, the person has been deceased for a minimum of 7 days. Though this method is effective, it has a downside that lies in the fact that as soon as the first generation of blowflies reaches adulthood, it becomes harder to determine which generation is present, and thus the first method must be used instead.
While Forensic Entomology seems like a relatively new invention, it does indeed have roots dating back to the 13th century. Renowned Chinese physician Song Ci wrote about it in his book, The Washing Away of Wrongs. Published in 1247, the book includes a story where a farmer's lifeless body was discovered in a field, bearing the marks of a sharp weapon. Every suspect was told to lay their sickles on the ground where one sickle, which contained a small trace of blood, attracted blowflies, eventually leading to its owner's arrest. The science of insect succession was founded in the 18th century by Jean-Pierre Mégnin, a forensic examiner who first tried to assess the concept of insect succession on corpses. Megnin formed the theory of the eight stages of insect successions on carrions and published his work in his novel La Fawne des Cadavers: Application de l’Entomologie à la Médicine Légale (also known as The Fauna of Corpses: Application of Entomology to Forensic Medicine- in English).
Despite the common belief that insects are insignificant creatures, they have proven extremely valuable in various fields, including criminal investigations. While it is only recently that we have begun to appreciate their importance, insects have been utilized in this field for centuries and will undoubtedly continue to play a crucial role in research for the foreseeable future.
Citations:
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insects in forensic investigations: An overview on the scope of forensic entomology”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296382/. Accessed 26 Feb. 2024
Khatoon, Sanweer, Kumar, Vikas, and Choudhary, Shweta. “Forensic Entomology: Insect
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