CSI PART 1: "Sex, Lies and Larvae"

23 January 2012

Solving Crimes...The Bug Way

(looking at a science project volcano)

Catherine: In fifth grade I built one of these as my science fair project, it was awesome. First place should have been mine, but they ended up giving it to this kid with some lame red ant colony.

(Grissom is smiling)

Catherine: That was you!

Grissom: Yeah, only my ants were black Argentineans.

Catherine: Uh-huh...

Grissom: I learned at a very early age that the bugs always win.

Catherine: Right...

That scene, taken from the oh-so popular hit television show CSI: Crime Scene Investigation features Catherine, a blood spatter specialist, and Grissom, a forensic entomologist, more appropriately known as "The Bug Man".

But does Grissom have a point? Do bugs really win all the time? To answer that question, we first need to dig a little deeper and a look a little closer into the world of bugs...

Perhaps you have wondered why on earth there are so many insects and other creepy crawlies. In fact, did you know there are more bugs, worms, and spiders than any other group of species on the planet!? What purpose could they possible serve except to annoy campers, barbequers, and, in some cases, spread disease?

Insects do the planet's dirty work, breaking down dead organic matter and returning it to the earth, ready to be used by new life. Over the years though, the job of insects has been harnessed to aid forensic scientists and police in the reconstruction of human activities and in the solving of crimes.

Did You Know?
Forensic entomology is the use of insects that feed on decomposing bodies to help in crime and other legal investigations The field of forensic entomology actually has three areas of investigation: medicolegal, urban, and stored product pests.

It is the medicolegal branch that you are probably most familiar with through the show CSI. Grissom is, in more specific terms, a medicolegal forensic entomologist, who uses insects that feed on decaying flesh to solve murders, but has also been know to run cockroach races just for the fun of it. But what is so special about bugs that they can help crack a tough case?

The insects are used by to give a 'time line' to the crime scene, answering questions such as how long ago was a murder committed, was the body was moved, and was the body wrapped in anything that might limit the insects' access to the body.

A "time line" can be drawn from the fact that insects develop in separate stages that are easily identifiable to the trained eye. For example, in blowflies, one of the first insects to arrive at a crime scene, the time of development from egg (or larva) to adult can take up to 3 weeks, depending on conditions.

Did You Know?
Insects undergo characteristic stages of development (from egg to adult) that can be used to help determine the time of death Typically though, adult flies can be found on a body within the first 10 minutes of death. Oviposition, or the laying of eggs, occurs within the first 8 hours. In fewer than 2 days, larva will have emerged which will then undergo 3 stages of development known as instars, and by the 4th or 5th day, will be full sized. By the 10th day, the larva enters a post-feeding stage and has developed a thick and opaque skin known as a puarium, to form a pupa. The adult finally emerges from this protective case to begin the life cycle once again.

So, as you can see, by working backwards from the time the bugs were collected and knowing the life cycle of a particular species of insect, an investigator can estimate the time of death, and pretty accurately too!

However, many other variables need to be considered, including temperature, sunlight conditions, and humidity, since all of these will influence the progression through to adult stages. Once all of the variables are incorporated into the scenario, the data obtained can be very helpful in solving a crime.

Did You Know?
A forensic entomologist also needs to consider other factors, like temperature and humidity, when using insects to help predict a timeline of events for a particular crime Urban entomology involves the insects that affect humans in their domestic environments. In this case, the entomologist must be familiar with the insects that feed not only upon the dead, but also the living and nonliving matter. The presence of certain pests within the walls of a building could signal negligence by the property owner, or insect bites may have been confused for signs of child abuse. The urban entomologist plays a vital role in solving these mysteries and often participates as a witness in civil proceedings due to monetary loss or damage.

Finally, stored product entomologists use biological information about the life cycle and distribution of pests in the world to help identify the origin of certain foods or other organic materials. Illegal trafficking of biological matter such as wood, meat, and plant matter, can be stopped by authorities if they are able to identify the source of that activity. Certain pests are indigenous to specific regions or countries, and entomologists use this information to track down the origin of any illegal shipping of organic goods.

So maybe Grissom was right after all: when it comes down to solving a crime, bugs can give investigators the winning edge.

Learn More:

If the creepy crawlies don't creep you out and you'd like to read more on forensic entomology, including some specific cases where insects were used to solve a crime, check out these great links:

CSI TV show website:


Forensice Entomology:


Shoshanah Jacobs is a PhD Candidate in Arctic Seabird Ecology at the University of Ottawa. She would like to think that she will one day graduate.

Photo credit: www.ew.com


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