The first aspect that insects are useful in solving a crime is determining time of death or postmortem intervals. Insects arrive on the body very soon after death. By determining their life cycles, and age it can help estimate time of death. There are four main types of carrion species that are found on a body: necrophagous, predators and parasites of the necrophagous, omnivourous insects, and hunting spiders. () The first group of necrophagous deals with insects that feed directly on the corpse. They usually depend on decaying remains as a food source, so they are very aggressive in their search for food. This is why they arrive at the dead remains only minutes after death. They include both flies and beetles.
Flies are usually the first to arrive to the deceased body. The most common one is the blowfly, which is metallic green or blue. Their life cycle is what helps to determine how long a body has been decaying. Their life cycle is developed in six stages. The first stage is the adult fly, which locates the body to feed and reproduce. Second, the adult fly lays eggs in mucosa membranes, so the eggs are near a food source. These membranes include the eyes, ears, nose, mouth, any open wounds, and the genitals or anus if they are exposed. They usually are not attracted to postmortem wounds, because they do not produce as much blood as perimortem or antemortem, because the heart is no longer pumping the blood. This occurs approximately twenty minutes are death. Then about ten till thirty hours later the eggs hatch with the first instar larva, which is about one to two inches long. It immediately begins to feed on tissue, and increase in size. They then shed their cuticle eleven to thirty-eight hours later to begin their second instar, which is complete in another eleven to twenty-two hours. After another twenty to ninty-six hours the third instar is molted and the larva begins to move away from the body. They move to a drier place away from predators, and parasites to pupate. This process occurs forty to five hundred and four hours later. At first it is a white or ellow color, and then turns to a reddish brown color. After four to eighteen days it becomes an adult fly, it rarely returns to the same body unless there still is a decent amount of tissue left. It usually begins producing five to eighteen days after it completes its pupate.
The other category of necrophagous is the beetles. They along with the flies are usually the first species to arrive to the body. They usually arrive after the body has dried. To differentiate between beetles and fly maggots, you need to look and see if they have any legs. Fly maggots do not have any legs, whereas beetle maggots have three pairs of legs. They are also either white robust and hairless, or dark brown, slender, and quite hairy.
The next types of carrion species are predators, and parasites of the necrophangous. The predators include bury beetles, rove beetles, and hister beetles. They eat the eggs and maggots other beetles and flies. Parasites are made up of ants, bees, and wasps. Small wasps are especially common on the body as a parasitic to the maggots and pupae of flies. They lay their eggs either inside or outside of the maggots or pupa. The eggs then...