Creepy Crawly Detectives

 

When you think of a crime scene, images of Sherlock Holmes, Tom Cruise, high-tech gadgets and police tape may come to mind. But what if I told you there were better detectives – although not as mysterious as Holmes or as handsome as Cruise – that could give crucial information for solving a difficult case? Move over, Ethan Hunt – these six-legged sleuths, with their bulging eyes and a taste for decaying flesh are literally crawling with information. In the field of Forensic Entomology, the presence of insects can provide information about an otherwise cold case (especially those that involve bodies that are physically cold and decomposing).

One of the most common uses of insects in forensics, is to decipher the post-mortem interval. The first insects to arrive at a dead body are normally Blowflies (Calliphoridae) or flesh flies (Sarcophagidae) (Anderson, n.d.). These bugs and other carrion insects have amazing olfactory systems, and are attracted by the scent of a decomposing body (Magni, 2023). They can take up to 24 hours to arrive, or can be found at the site in a matter of minutes. These insects, with their short lifespan, are driven by the need to secure a suitable habitat to lay their eggs. A dead body is the perfect protein-rich, warm, moist, environment on which to oviposit (Stetler, 2013). The usefulness of these insects in forensics comes from the predictability of their lifecycle. After an egg of a Blowfly has been laid, it hatches in the next 8-12 hours. From that stage follow three instar stages and a pupa stage before the fly larva becomes an adult. Each of these developmental stages is distinct, and can often be distinguished based on the number and size of spiracles on the maggots (Blowfly larva) (Anderson, n.d.). Even if the body is discovered after the flies have hatched and become adults, empty pupal cases are left behind indicating the lifecycle has been completed (Anderson, n.d.). The stage of the lifecycle the Blowflies are in allows forensic scientists to calculate the post mortem interval of a body.

The short life cycle of a Blowfly.

 As a dead body stagnates, different species of bugs will find their way to the carnage. While some (like Blowflies and Flesh Flies) are attracted to the carnage while it is still fresh, other families like the Piophilidaes (or cheese skippers) approach when active protein fermentation begins to take place (Anderson, n.d.). Knowing this allows forensic scientists to use this information to gain more evidence about the post-mortem interval (Matuszewski & Mądra-Bielewicz, 2025). However, in order to accurately predict this, it is also necessary to have knowledge of how different bugs develop under specific conditions – such as hot or cold weather, being indoors or outside, or how their growth is effected by the presence of different drugs (Osterloff, 2022). Scientists in human taphonomy facilities work to examine how the human body decomposes, how maggots and other bugs react to changes in their conditions, and how this effects their lifecycle (Osterloff, 2022). From this information, forensic scientists can determine the approximate amount of time that has elapsed since the death with a good amount of accuracy (Osterloff, 2022).

A Blowfly on a piece of carrion (Picture credit: Natural History Museum).

Awareness of flies and their natural habitat also assists in understanding complicated crime scenes. If a forensic scientist is aware of local insects, they can tell if bodies have been moved from one location to another. If certain insects are non-native to the habitat in which the body is found, the flies present can give clues to the location where the murder actually took place (Anderson, n.d.).

 Carrion insects aren’t the only ones that assist in forensic entomology. Bed Bugs, or Cimex lectularius can also be used for identification purposes (Charuchandra, 2024). If bed bugs are found near or around a crime scene, forensic analysis can dissect these bugs in order to retrieve blood from their last meal. They can then use this blood sample to compare with the blood of suspects to determine if they have a match (Charuchandra, 2024). Analysts can also use the blood found in bedbugs to extract DNA, and use this to identify victims and suspects in different types of criminal cases (Charuchandra, 2024). This type of sampling is best done before the bedbug has fully digested its last meal – giving analysts about 12-72 hours to collect the most accurate results and complete DNA profiles (Charuchandra, 2024). Even if partial profiles are only able to be collected from these blood samples, this can still assist forensic scientists in identifying and ruling out suspects (Charuchandra, 2024).

Picture of a Bedbug. The blood meals found in these insects can be used for forensic investigations (Picture credit: Wikepedia).

Insects found on dead bodies can also be tested to see if they contain trace amounts of different drugs. This can help identify the cause of death, and lead to knowledge of various other factors in a crime investigation (Department of Entomology, 2025). Since the human body quickly flushes out any evidence of drugs, testing insects that have fed upon decomposing tissue or blood are a more reliable indicator of drug use (Department of Entomology, 2025). Additionally, other insects are indicative of poor living conditions or neglect (such as fleas or lice) (Department of Entomology, 2025). Flies associated with wounds or uncleanliness as well as those that are attracted to dead bodies, may give clues on events leading up to the death, or conditions that were present before death (such as abuse or neglect) (Department of Entomology, 2025).

When we encounter bed bugs, maggots and blowflies on a daily basis, we see them as pests, or as gross bugs capable of carrying disease, or indications of uncleanliness. But, for a forensic scientist, these creatures cause a stir of excitement. While we would call an exterminator, a forensic scientist on a murder case would see these bugs as giving crucial information on the time, place and cause of a death (Matuszewski & Mądra-Bielewicz, 2025).

 

 References

Anderson, G. (n.d.). Forensic Entomology: The use of Insects in Death Investigations. Simon Fraser University. https://www.sfu.ca/~ganderso/forensicentomology.htm#:~:text=Tel.%20%28,determine%20elapsed%20time%20since%20death.

Charuchandra, S. (2024, January 13). How bed bugs might help crack criminal cases. Advanced Science News. https://www.advancedsciencenews.com/how-bed-bugs-might-help-crack-criminal-cases/#:~:text=%E2%80%9CInsects%20play%20a%20crucial%20role,researcher%20at%20Murdoch%20University%20who

Department of Entomology. (2025, February 20). Maggots and murder: What insects can teach us about crime. University of California . https://entomology.ucr.edu/news/2019/04/29/maggots-and-murder-what-insects-can-teach-us-about-crime

Magni, P. (2023, July 10). When remains are found in a suitcase, forensics can learn a lot from the insects trapped within. Route Fifty. https://www.route-fifty.com/infrastructure/2022/09/when-remains-are-found-suitcase-forensics-can-learn-lot-insects-trapped-within/376552/?oref=rf-next-story#:~:text=As%20we%20opened%20the%20suitcases,can%20help%20us%20solve%20crimes.&text=This%20article%20is%20republished%20from,Read%20the%20original%20article.

Matuszewski, S., & Mądra-Bielewicz, A. (2025). When insect development meets insect succession: Advantages of combining different methods and insect taxa in estimating the post-mortem interval. Forensic Science International: Synergy, 10, 100574. https://doi.org/10.1016/j.fsisyn.2025.100574

Osterloff, E. (2022). Murder, maggots and forensic entomology. Natural History Museum. https://www.nhm.ac.uk/discover/murder-maggots-forensic-entomology.html

Stetler, C. (2013). Fly away: Rutgers entomologist studies blow flies and crime scenes. Rutgers University. https://www.rutgers.edu/news/fly-away-rutgers-entomologist-studies-blow-flies-and-crime-scenes#:~:text=Blow%20flies%20are%20attracted%20to,lifespan%20of%20about%20a%20month.