What is a maggot?
A maggot is a squishy, wiggly fly larva that you may see on road kill or in a garbage bin. They seem gross and icky and they imply that something is rotting, which is also gross. Maggots are not a welcome sight in our homes (or otherwise), but they are important creatures in nature and for the forensic scientist.
So why are maggots cool? So many reasons! They are resourceful, solve crimes, and flies can sense death. These useful little buggers (pun intended) are fascinating and forensically useful. First, to understand what makes maggots so cool, we have to understand the life cycle.
The Life Cycle
Flies are incredibly perceptive. If a creature dies, a fly is often the first to know. When something dies outside, almost instantly a fly will land on the corpse/carrion to deposit eggs. The wild part is that we have no idea how they sense death, but they do and they are consistent about it. So consistent in fact that they can help forensic scientists predict time of death.
The blowflies are a common, recognizable fly. They can be beautifully iridescent and are often found near anything that is rotting. The female blowfly first lays its eggs in a cavity, open wound, or any soft, squishy place. The maggots then hatch from these eggs and begin to feast on anything that is soft and squishy. As they eat, they grow. These larval stages are called instars. The maggot then looks for a dark protected place to pupate and creates a hard shell in which to develop into an adult fly, just like a caterpillar that forms a cocoon before becoming a moth. The adult fly then emerges from the pupa to start the cycle again.
The life cycles of these insects are so predictable that forensic experts use them to count backward to the time of death. But how?
Maggots Determine Time Of Death
Let’s say you stumble across a dead body in the woods. You call the police and the police notice that there are maggots on the body. The resourceful investigator would then go to the store and buy a pound of hamburger for them to eat. The maggots are collected and given hamburger to eat. Maggots get hungry and we don’t want to retard their life cycle. The maggots and the hamburger are then given to a forensic entomologist (bug doctor) who will continue to feed the maggots until they become flies. A species of fly can only be determined with certainty once it is in the adult stage, since many maggots of different species look similar. So, once the species is known, the entomologist can count backwards to determine when the female fly first laid the eggs (see Blowfly Life Cycle pic). Since flies are so amazing at detecting death, the results can be surprisingly accurate.
This technique requires information about the weather, a temperature controlled labs, and a way to identify the species. It’s not al simple process but it can have a really useful outcome for investigators.
The times that this doesn’t work is when a body has been exposed for a long period of time, especially greater than 2 weeks. There may still be maggots on the body, but there’s no way to know what generation they are. The maggots could have hatched, pupated, and developed into flies a half dozen times before the body was found. The fresher the body, the more accurate the results.