Decomposition - Succession

The environment provided by a dead body changes with time. 

Intestinal Bacteria

Intestinal Bacteria
Photographer: D. Colgan © Australian Museum

This change is a result of drying, and the activities and by-products of the corpse fauna. Different groups of animals find the corpse attractive at different stages of decomposition and the resultant change in the animal community is called a succession.

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.

Flies have great powers of dispersal and they rapidly discover bodies, usually* ahead of the beetles. Although they can feed on fluid that exudes from a fresh body, the acidic tissues of a fresh corpse cannot be digested by flies. The activities of the bacteria, and the excretions of fly larvae feeding on exuded fluid, eventually neutralise the acid making the semi-liquid corpse particularly attractive to blowflies, flesh flies and house flies.

*(Necrophorus beetles carry mites on their bodies (Poecilochirus) which feed on fly eggs. If the mites arrive before the eggs hatch, the carcass can be dominated by the beetles.)

The alkaline environment created by the flies is toxic for beetles and so beetles are largely excluded from feeding on the dead body itself as long as the fly larvae are active. However, many species of rove beetle, carrion beetle and burrowing beetle are still present in the early stages of decomposition because they are active predators of fly larvae, avoiding the alkaline tissues of the corpse.

Parasitoid wasps are also abundant at dead bodies, laying their eggs inside fly larvae and pupae.

As the corpse dries, it becomes less suitable for the blowflies, flesh flies and house flies that like a semi-liquid environment. Different fly families, the cheese flies and coffin flies, are abundant as the corpse dries.

Eventually, the corpse becomes too dry for the mouth hooks of maggots to operate effectively. The hide beetles, ham beetles and carcass beetles, with their chewing mouthparts, devour the dry flesh, skin and ligaments. Finally, moth larvae and mites consume the hair, leaving only the bones to slowly disintegrate.

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Tags death, decomposition, corpse fauna, succession,