Entomology PART ONE
(P2 will discuss how entomology is used in death investigations)
When a body dies, human or animal, it begins to decompose. In the beginning it can be very difficult to see any signs of decomposition. Of course, just as with other situations, the scene (inside or outside, temperature, etc) play a very big factor in how quickly decomposition begins to happen. However, insects and animals have such a hyper sense of smell, they seem to know within minutes. Flies show up very quickly and are usually the first to arrive. Obviously, if a person dies in a clean house, with no open windows or doors where flies have access to enter, then the flies are delayed. If there is someone else in the house and the authorities are notified quickly, then it is unlikely flies will have access to the body.
In a different scenario, such as a house in which the person is alone, and has an open window which does not have a screen, or an open slider without a screen, then flies have quick and easy access. In a short amount of time, flies will enter and explore the body. If the body is dressed or perhaps covered in bed where mostly the neck and face are the only areas easily accessible. If the body is uninjured, then the flies will go to the eyes, nose and mouth and occasionally the ears. They will find a warm, moist place and lay their eggs.
If the body is inside, completely naked and the flies have access to come inside they will go for they usual eyes, nose and mouth, but they will also go for any other warm moist areas they can access. If the house is in bad shape, such as a hoarder house, there will also be ants, cockroaches and rodents already in the house which will also investigate the body but will be interested in it as a food source more than to lay eggs. Ants often leave tracks of little bite marks which can often be wrongly thought to be abrasions or scratches. Because the person is dead when the ants bite, there is no swelling or inflammatory response.
If the body is outside, then the flies and other local insects will come right away. The hotter the temperature the faster the eggs laid by the flies will mature. If there are any wounds, the flies will concentrate there as well as the usual places I mentioned previously.
There are so many variables when using forensic entomology to make determinations in the investigation. It is very important to photograph the body with the insects in place before collecting specimens. Then carefully log them as you collect. One area at a time, collect live specimens as well as specimens to be preserved at their current stage. Log and photograph as you go as well as labeling each collection container.
In order to better understand the daily growth patterns, I grew maggots in my yard with a controlled environment. I photographed and documented daily. I used animal liver that I obtained from the market and did not disrespect any persons in order to carry out my experiment.
The following photos are from my experiments from growing fly maggots at my residence.
You can see flies on the fresh specimen as they lay eggs.
Eggs in their early stage. Can usually be seen in 24 hours or so. They are usually laid in a mass, as you can see in the lower right of the photo.
This is a piece of the liver after the maggots have been feeding off of it. You can see it is desiccated or dried out.
Through the photos you can see the maggots changing as they grow. When they are ready to change they crawl under something or into the dirt and their outer layer becomes a hardened shell. This is called the Pupa stage.
The flies emerge in about 2 weeks depending on the weather and conditions of their surroundings. In the photo above you can see a green bottle fly and a gold bottle fly that emerged from the casings.
Some of the tools I keep in my collection kit.
In part 2, I will discuss how entomology can be used in death investigations.