Free online Course on Basics to Forensic Entomology
FREE online courses on the Basics to Forensic Entomology - Analyzing the
crime scene - Introduction
The feature with arthropods that is most important in medico
legal 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
(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. Which is discussed in detail later in this course.
If we know how long it takes to reach the different stadiums
in an insect's 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 tire 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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