The young maggots move throughout the body, spreading bacteria, secreting digestive enzymes and tearing tissues with their mouth hooks. They move as a maggot mass benefiting from communal heat and shared digestive secretions. Skeletonised human remains near the entrance to the Forensic Anthropology Center at Texas State University in San Marcos, TX. Photograph: Mo Costandi

Decomposition notebooks are environment-friendly as they are made from recycled waste materials, while not all composition notebooks are made from recycled materials. Age Decomposition begins several minutes after death, with a process called autolysis, or self-digestion. Soon after the heart stops beating, cells become deprived of oxygen, and their acidity increases as the toxic by-products of chemical reactions begin to accumulate inside them. Enzymes start to digest cell membranes and then leak out as the cells break down. This usually begins in the liver, which is enriched in enzymes, and in the brain, which has high water content; eventually, though, all other tissues and organs begin to break down in this way. Damaged blood cells spill out of broken vessels and, aided by gravity, settle in the capillaries and small veins, discolouring the skin. Once self-digestion is under way and bacteria have started to escape from the gastrointestinal tract, putrefaction begins. This is molecular death – the break down of soft tissues even further, into gases, liquids and salts. It is already under way at the earlier stages of decomposition, but really gets going when anaerobic bacteria get in on the act. The study was carried out at the Southeast Texas Applied Forensic Science Facility in Huntsville. Opened in 2009, the facility is located within a 247-acre area of National Forest, which is owned by the university and maintained by researchers at Sam Houston State University (SHSU). Within, a nine-acre plot of densely wooded land has been sealed off from the wider area, and further subdivided, by 10-foot-high green wire fences topped with barbed wire. Kamal, A.S. 1958. Comparative study of thirteen species of sarcosaprophagous Calliphoridae and Sarcophagidae (Diptera) I. Bionomics. Annals of the Entomological Society of America. 51: 261-270.Even if colonization does occur just after death, estimates based on insects’ age may be inaccurate for another reason. Insects are cold-blooded, and so their growth rate occurs relative to temperature rather than to the calendar. “When using insects to estimate post-mortem interval, we’re actually estimating the age of the maggot and extrapolating from that,” says Bucheli. “We measure insect birth rate by accumulated degree hours [the sum of the average hourly temperature], so if you know the temperature and the growth cycle of a fly, you can estimate the age of a fly within an hour or two.” Each fly deposits around 250 eggs, that hatch within 24 hours, giving rise to small first-stage maggots. These feed on the rotting flesh and then molt into larger maggots, which feed for several hours before molting again. After feeding some more, these yet larger, and now fattened, maggots wriggle away from the body. Then they pupate and transform into adult flies, and the cycle repeats over and again, until there’s nothing left for them to feed on.

According to one estimate, an average human body consists of 50-75% and every kilogram of dry body mass eventually releases 32g of nitrogen, 10g of phosphorous, 4g of potassium, and 1g of magnesium into the soil. Initially, some of the underlying and surrounding vegetation dies off, possibly because of nitrogen toxicity, or because of antibiotics found in the body, which are secreted by insect larvae as they feed on the flesh. The variations may also be related to differences in the period of time that had elapsed since death. An earlier study of decomposing mice had revealed that although the animals’ microbiome changes dramatically after death, it does so in a consistent and measurable way, such that the researchers were able to estimate time of death to within 3 days of a nearly 2-month period. Many bacteria respire anaerobically (without oxygen) and so they can consume the body from the inside. They are also tolerant of the acidic conditions of the muscles shortly after death, caused by the build up of lactic acid. Because of these attributes and the fact that they are already present in the body before death, bacteria are the first colonisers and they continue to feed on a dead body until it dries out. A large volume of body fluids drain from the body at this stage and seep into the surrounding soil. Other insects and mites feed on this material.

The speed of the chemical reactions involved doubles with every 10°C rise in temperature, so a cadaver will reach the advanced stage after 16 days at an average daily temperature of 25°C, and after 80 days at an average daily temperature of 5°C. Composition notebooks are empty notebooks commonly used by students for writing, while decomposition notebooks are a new variety of composition notebooks having fun prints and are made of recycled paper. Cover In late 2011, SHSU researchers Sibyl Bucheli and Aaron Lynne and their colleagues placed two fresh cadavers here, left them to decay under natural conditions, and then took samples of bacteria from their various parts, at the beginning and the end of the bloat stage. They then extracted bacterial DNA from the samples, and sequenced it to find that bloating is characterised by a marked shift from aerobic to anaerobic species.

All of our samples came from criminal cases involving people who died by suicide, homicide, drug overdose, or in traffic accidents,” she explains. “Taking samples this way is really hard, because we have to ask the [bereaved] families to sign our consent forms. That’s a major ethical issue.” Every species that visits a cadaver has a unique repertoire of gut microbes, and different types of soil are likely to harbour distinct bacterial communities, the composition of which is probably determined by factors such as temperature, moisture, and the soil type and texture.lactic acid - an organic acid produced in mammals during the breakdown of glucose when oxygen is in short supply.