Dr. Sperling is a Professor of Entomology at the University of Alberta. He has done lab research using DNA to identify flies and maggots, which will allow for faster identification of a species - and in forensics, time is of the essence. Dr. Sperling provided his expertise for Giles Blunt during the writing of Blackfly Season. BOOKED and The Alibi got to do the same. Squeamish be warned, today we're talking maggots.
"The cycle of insects on a body, starting from death and ending with the last insects leaving, is a very complex chronology," begins Dr. Sperling, pulling out a blue plastic bucket containing some liver. "Generally speaking, however, the first things to find the body will be blow flies. Blow flies are very good at detecting absolutely fresh corpses. They don't eat them, though - flies exist to disperse and lay eggs. They live off of the food they ate during the maggot phase of their life cycle." At this point, Dr. Sperling lifts up a black piece of liver to expose greyish maggots writhing under the meat and amongst the sawdust substrate. [We warned you! --Ed]
"Maggots are eating machines, and it is these that eat the flesh and use the fluids. After these first flies have begun their cycle, other insects will start to arrive and lay eggs. These newcomers often have predacious maggots - they will eat the blow fly maggots. After these, you will find flies such as cheese skippers which feed on fatty areas or dried areas of the body, and finally, after weeks or months, you will get beetles. Beetles have strong mandibles and are very good at scraping away at things. They will sometimes be on the corpse for a year or two before they finish scraping what they can."
From this very general timeline, investigators can get an idea of how long it has been since the body was left outdoors undisturbed. We left Dr. Sperling as he put his maggot farm back in a well-ventilated storage unit, cheerfully remarking that "it's important to put them into a place where there's a strong fan so that the rest of the building doesn't get too upset with the smell of these being here."