Flies are often annoying: they fly over food, rest on the body and buzz. However, they constitute a fundamental piece when it comes to unraveling the mysteries that involve a crime, because they are the first insects to arrive and colonize a decaying body. It is not just about humans, but covers all types of vertebrates such as reptiles, birds, fish, amphibians and mammals. Studying the fauna that arrives at the corpses allows us to obtain information about how and when that living being died, and forensic entomology takes care of that.
O Scientific news agency of the National University of Quilmes visited the Laboratory of Applied and Forensic Entomology this house of studies to discuss the work they do. “We investigated which are the species of flies that colonize decomposing bodies because allow us to find out when was the approximate date that this organism died”, tells the Agency Monica Chirinodirector of the Laboratory and professor at UNQ.
When a corpse is exposed to the action of insects, they begin to colonize it.: Flies lay eggs, which later turn into larvae and feed on the body. Later, other types of fauna arrive, such as beetles and flies of different species.
Chirino explains that “Studying flies allows us to travel through time”, and exemplifies: “If we find a body, which is unusual, it will have certain characteristics. It can be recently or long ago, naked or clothed, stabbed or buried. What we have to find out is how long that body has been there. Thus, as flies are the first to detect it and to deposit their eggs which will later become larvae, we must identify the species in question and compare it with the data we have in the laboratory”.
Depending on where and time of year the vertebrate dies, the types of flies that lay eggs first will be. Thus, for example, in the urban area of the south zone of Buenos Aires, the most abundant flies are called “Lucilia sericata” (metallic green fly) and “Lucilia cuprina” (bronze colored fly) and, to a lesser extent, “Lucilia ocricornis”. .
In this context, the Conicet researcher also continues the example. “There are flies that are rural and others that are urban. Then, if the body appears in the field, but it has city fly eggs, it means it has been moved and it is not there where the death occurred, as well as if it has eggs or larvae from the heat and it is already cold, it means that it died recently”.
Do they survive in water?
At the Laboratory of Applied and Forensic Entomology, Lucila Salanitrograduated in Biotechnology at UNQ and doctoral candidate at Conicet, investigates the development of larvae of the fly Lucilia sericata in the context of submersion. interviewed by this halfreports the researcher: “We found that The eggs of this fly (which remain in the air) survive in water for up to six hours and their development to become larvae is not affected.”.
“It’s a partial submergence, that is, once inside the water and once outside. It is as if a body had been thrown into the river and the tide had brought it up. What these results allow is consider the possibilities. For example, if the eggs didn’t survive, it’s because the body was submerged for more than six hours.or if the eggs of this species of fly that is not aquatic are present, it is because the body died on land and then went into the water”, details Salanitro.
To arrive at this result, the researcher placed mother fly eggs on pieces of meat, submerging them at different heights (25 cm, 15 cm and 5 cm) and at different time intervals. He then removed them and allowed the vital development of the larvae to continue at room temperature.
mushrooms also help
If the investigation carried out by Salanitro begins at the moment of death of the body, that of Anabella Massaccesi He is across the road when several years have passed since his death. She is doing her graduate work in Biotechnology in this lab and characterizes different fungi that appear in bone remains after a long time buried. For that, works in the exhumations that are carried out in the Cemetery of Ezpeleta.
“The idea is to be able to determine how long the person has been buried. We’re talking years, so sometimes there’s skeletal remains, like a jawbone, and sometimes there’s nothing left.”, explains Massaccesi to the Agency. He continues: “From time to time, the cemetery transfers the remains of graves to a mass grave. Then, with the necessary permissions, I take the bones, I scrape them off with sterile cotton swabs and take these samples to the lab.”.
Through different materials, the thesis student evaluates the development of each fungus and makes a characterization. “The problem is that the vast majority of fungi are not known, Forensic mycology is not developed all over the world, and in Argentina there are only three people specialized in it. So my job is to characterize the fungi and compare them. I work with fungi from bone remains from more than forty years, twelve years and three months to find out if they change or if they are the same”.
From micro to macro, forensic entomology works with tiny elements that are of vital importance in the extensive joint work of detectives, police and judges.