Using forensic entomology to determine whether the body has been moved after death
After death, a succession of fungi, bacteria and animals will colonize the dead body. The substrate on which the body is lying will also change over time. Leakage of fluids from the dead body will lead to the disappearance of certain insects, and other insects will increase as the time goes. A forensic entomologist can then look for how long the body has been there by looking at the fauna at the body, and also estimate the time the body has been lying there by sampling soil insects underneath the dead body. If there is a difference in the estimates, and the analysis of the soil suggests a short PMI, and the analysis of the body fauna suggests a longer PMI, one can suspect that the body has been moved. One can also see that a body has been lying at a particular place long time after the body has been removed, both by botanical means, and by analysis of the soil fauna.
Some times dead bodies are found in concealed environments, where blowflies have no access. If there is blowflies, it means that the body has been moved there. Some Calliphorids are heliophilic, that is, they prefer to lay their eggs on warm surfaces, which means that they usually occur where the bodies lies in sunny places. Other blowflies prefer shade. For example, Lucilia species prefer sunlight, and Calliphora prefer more shady conditions. Some species are synanthropic and occurs in urban areas, other species are not synanthropic and occurs in rural areas. Calliphora vicina is a synantropic fly, very common in cities, and Calliphora vomitoria is a more rural species, seldom caught in cities.