Insects: Beautiful and Important

You have undoubtedly encountered insects before. Whether on a nature walk or in a bustling city park, you have likely come across bees, flies, butterflies, or beetles in their natural surroundings—hovering near flowers, strolling through the grass, or climbing a fruit tree. Insects, the most abundant and successful terrestrial animals on Earth, thrive in almost every corner of the planet, except for the oceans. While some insects, such as bees, ants, or mosquitoes, can be seen as enemies of humans because of their defensive bites or stings and, in some cases, their role as disease carriers, it is important to recognize their vital roles in maintaining healthy ecosystems.

The specialized field within biology that studies insects is called entomology, and the professionals who study this fascinating topic are called entomologists. Entomologists possess extensive knowledge about insects: where they live, how long they live, what they eat, and how long it takes for them to develop from eggs to adults (Figure 1).

Insects as Crime Scene Clues?

Beyond the ecological importance of insects, such as bees pollinating flowers for fruit production, did you know that certain insects can assist detectives and the justice system in solving crimes? Thanks to the expertise of entomologists, questions like “how long ago did this murder occur?” or “how long have termites been living in my house?” can be answered. This is called forensic entomology [1, 2]. There are real life examples of insects serving as clues in cases of various legal problems, such as understanding who is responsible for food contamination, home infestation, or even understanding how a person died after ingesting a banned substance or poison, among others [3].

Crimes Involving Homes

Consider this scenario: you and your family have moved into a new house, and you excitedly begin to hang a photo on the wall. However, upon inserting the first pin, you discover termites inside the wall, damaging the house’s structure. As a result, your family files a lawsuit against the company that sold the house, claiming that it was infested with termites before they bought it. The question that arises is “How long have these termites been living there?”. By studying the termites, an entomologist can estimate the colony’s age and provide crucial evidence to determine if they were present before or after your family bought the house. This is an example of an urban forensic entomology case, in which insects like beetles, ants, and termites are used to solve these crimes (Figures 2B, C, E).

Issues of Food Contamination

Now imagine you are about to enjoy a delicious chocolate bar. You open the package only to find insect larvae on the candy! How long have these larvae been there? Where did the contamination happen? Did the insects get into the chocolate bar at your house, did contamination happen at the market, or was it the result of carelessness by the food manufacturer? An entomologist, after studying morphology, length, weight, and preferential habitat of the insect, along with information about the time between the purchase of the chocolate bar and when the larvae was found can answer such questions. This is an example of a forensic entomology case for stored products or other goods. Flies, beetles, moths, cockroaches, and ants are generally involved (Figures 2A–D, F).

Illegal Animal Smuggling

Now, picture yourself as a police officer working at a major airport. You observe a passenger illegally transporting a box containing numerous insects, which you believe the passenger intends to sell. This is a case of animal trafficking, which is illegal around the world. How can you determine where the insects came from if the passenger remains silent? By identifying the insect species and its natural habitat, an entomologist can help gather valuable information about where the smuggled insects came from, and can also reveal whether the insects are an uncommon or rare species, which would make the crime even more serious.

Violent Deaths

One of the most studied and well-known areas of forensic entomology focuses on the role insects play in helping experts solve crimes involving violent deaths [4]. In such cases, insects can provide crucial answers to questions like “who is the victim?” or “how long ago did the death occur?” or “where did the homicide take place?”. But how is all this information obtained from insects?

Now picture yourself as a detective called in to solve a crime. When you arrive at the crime scene, you see the victim lying on the ground. As you look closer, you notice some fly maggots around the body. You carefully collect some of the insects to show to an entomologist. The entomologist identifies the species and provides details about life cycle, size, and weight of the larvae you found. Information about the fly’s habitat, for example, can tell you about the location where the murder occurred.

Further, information about the size and weight of the maggots can also provide details about how much time passed between the time the crime was committed and when the body was found, which is known as the post-mortem interval (PMI) [4]. Following death, the human body begins a lengthy decomposition process. During this time, the chemical elements present in the skin, bones, nails, and hair, such as carbon and nitrogen, are reabsorbed into the Earth. This decomposition process attracts various species of necrophagous insects, drawn by these chemical elements, even from kilometers away! These insects feed on the decomposing matter and lay their eggs or larvae there, continuing their species’ life cycle.

For instance, a fly might discover a corpse on which it lays its eggs. These eggs then hatch into larvae, which feed and grow. The growing larvae pass through three stages and then seek out a safe (and typically dark) place to enter the next stage of development, known as the pupal stage—similar to the cocoon stage of a butterfly. Eventually, an adult fly eventually emerges from the pupa (Figure 3). This entire process, from egg to adult, takes a specific amount of time for each species, and can be influenced by environmental factors such as temperature and humidity. Therefore, by identifying the type of larvae found on a corpse and studying its size, weight, and structural characteristics, entomologists can estimate the larva’s age [5]. This expertise allows entomologists to provide vital information like PMI, in the form of a report that can be submitted as evidence to the court to aid in convicting or acquitting a suspect.

Seeing Bugs Under the Light of Forensics

Based on what you have learned, you might realize that insects are even more important than you thought! Besides all their critical roles in ecosystems (as pollinators, pest control, decomposition, and in nutrient cycling, for example), some insects can be crucial clues used in solving several types of real crimes. However, the loss of insect populations due to habitat destruction, pesticide use, climate change, and other factors poses significant threats to ecosystem stability and biodiversity. We need to work hard to preserve insect diversity and the essential ecological functions these amazing creatures provide—including crime scene investigation. Remember this cool role of insects the next time you see a bug in nature!

Glossary

Insects: ↑ A group of animals with six legs, one pair of antennae and two pairs of wings.

Entomology: ↑ A branch of science that study insects.

Justice System: ↑ A group of organizations that make sure people follow the law.

Forensic Entomology: ↑ The study of insects to help solve crimes. “Forensic” means using scientific methods to investigate and solve legal cases.

Contamination: ↑ Presence of impure or harmful entities which can cause consumer illness as well as degrade the quality of food.

Animal Trafficking: ↑ The unethical and illegal transport and sale of animals.

Post-Mortem Interval: ↑ The time interval between death and discovery of the body.

Necrophagous Insects: ↑ Insects that feed on decomposing animal matter, such as dead corpses.

Larvae: ↑ The immature form of some insects, such as flies, beetles, ants.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

We would like to thank our young reviewers and their respective science mentors for their amazing opinions and criticisms, which improved the quality of the manuscript.