Brazoria County Sheriff's Office

Identification Division

What is Forensic Entomology?

Forensic entomology can be said to be the application of the study of insects and other arthropods to legal issues. It can be divided in three subfields: urban, stored-product and medicolegal. It is the medicolegal aspect that I will discuss in this document.

Medicolegal forensic entomology includes arthropod involvement in events such as murder, suicide and rape, but also includes physical abuse and contraband trafficking.

Since the earth is a predominantly arthropod world, it is not uncommon that we mere humans comes in contact with these creatures. They make the world go round, as they pollinate, eat other arthropods, eat living plants and trees, dead plants and trees, living vertebrates, dead vertebrates and vertebrate dung and urine and a lot of other things.

The feature with arthropods that are most important in medicolegal forensic entomology is that they are important carrion feeders, that is they eat dead vertebrate bodies, including man. Thus they perform a valuable recycling of organic matter in our ecosystem.

One of the first groups of insects that arrive on a dead vertebrate is usually blowflies (Diptera: Calliphoridae). Usually the female oviposits within two days after death of the vertebrate. Then the blowfly goes trough the following stadiums: egg, 1. instar larvae, 2. instar larvae, 3. instar larvae, prepupae, pupae within puparium, imago.

If we know how long it takes to reach the different stadiums in an insects life, we can calculate the time since the egg was laid. This calculation of the age of the insects can be considered as an estimate of the time of death. But even if the estimate of the insect age is correct, the death of the victim (usually) occurred before the eggs were laid. This period is quite variable and depends on temperature, time of day the death occurred, time in year the death occurred, whether the corpse is exposed or immersed in soil or water. As a general rule insects will lay eggs on a corpse within two days after the corpse is available for insects.

Insects can also be of help in establishing whether the corpse has been moved after death, by comparing the local fauna around the body, and the fauna on the body.

In some instances, movement of suspects, goods, victims or suspect vehicles can be traced with the help of insects. Insects parts, or whole insects can for example be captured in different car parts, such as in radiators or tyre treads. By identifying the insects found, and plotting the distribution of each insect, as well as the biology of each species one can find the greatest degree of overlap, and describe the areas where the suspect has been.

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