Click on a square to learn about the basics of Forensic Entomology 1. When a body dies, it quickly begins to decompose through a process called autolysis. This breakdown produces gasses that escape through the natural orifices. These gasses attract certain kinds of insects that feed on decomposing tissues. The scent of blood from open wounds also attracts these creatures, and they sometimes arrive within minutes of death. TOP
2. As the body decomposes it releases a progressive series of chemical indicators, and each attracts a different species of insects. The first to arrive at the death scene are usually blowflies (family Calliphoridae). Pregnant female blowflies lay their eggs in soft, moist tissues such as those around natural openings and exposed wounds, since the larvae that hatch from the eggs are unable to penetrate healthy adult skin. TOP
3. When the eggs hatch, tiny cream-colored larvae emerge, commonly called maggots. These maggots begin to feed on the soft surrounding tissues, scraping off decomposing tissue using a pair of tiny mouth hooks. As the maggots grow they pass through three distinct stages, called instars. In the third instar the maggot ceases to feed and prepares to pupate, or mature into an adult fly. It begins to shrink slightly and its skin darkens, and it may crawl away from the body to find a safe, secluded spot to mature. TOP
4. Through studies on decomposing remains in various conditions, forensic entomologists know exactly how long it takes each species of insect to reach various stages of development. At a death scene, an entomologist collects a representative sample of the maggots present at all areas of infestation. In a laboratory he will rear some of them to maturity, carefully noting the time required until the adult fly emerges. Counting backwards, the forensic entomologist is then able to estimate precisely when the eggs were first deposited on the body. TOP
5. Once the forensic entomologist determines when the eggs were first oviposited, he must consider a series of environmental factors to estimate the actual time of death, such as time of day, ambient temperature, and availability of the body to insects. The entomologist always collects weather data from the nearest weather station, and may return to the death scene several times to take temperature readings himself. TOP
6. By the time the maggots have fed on the softer tissues and crawled away to pupate, the body has dried out too much to interest other blowflies and flesh flies. Now other species of insects begin to arrive in a predictable order, a process known as faunal succession. Hide beetles, for example, consume cartilage and dried skin but dislike moist tissues. After the first two weeks of decomposition, faunal succession is crucial in estimating time of death. TOP
7. Forensic entomology is most commonly employed to estimate post-mortem interval; after seventy-two hours, it is the most quantifiable way to determine time of death. But forensic entomology has also been used in cases involving child abuse, nursing-home neglect, drug smuggling, and contraband trafficking. TOP
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