There's no quicker way to elicit a shiver of disgust than to mention maggots. Halloween brings maggot-filled tricks and treats, from cupcakes to faux maggots for zombie costumes. But maggots are more than creepy, crawly insects.

Maggots, which are actually the larvae of flies, have helped doctors clean wounds on and off the battlefield since Napoleon's time. Now, they're also helping to catch criminals. Forensic entomology—the study of how insects interact with dead bodies—can help law enforcement and lawyers in criminal investigations, and maggots are a big part of that.

The presence of flies or maggots on a dead body can give researchers a sense of when a person or animal died, and whether the body was moved from one location to another, said Jeff Tomberlin, a forensic entomologist at Texas A&M University in College Station. Hundreds of insect species can be involved in breaking down a dead body, but flies and beetles are the "major players," he said.

Flies Come First

When an animal dies, microbes begin to break down its tissues and produce gases, Tomberlin explained. This is what makes corpses bloat. Then come the insects.

"Typically the first things to show up are the flies," the forensic entomologist said. Blowflies, flesh flies, and black soldier flies are typical species found on vertebrate remains.

The flies home in on moist cavities like the mouth, nose, and eyes to lay their eggs. The young that hatch out are the maggots, which proceed to eat their way through the surrounding soft tissue.

Different fly species have different dietary requirements, Tomberlin explained. The black soldier fly maggots in the video (above) are omnivorous, meaning they can eat a wide variety of foods, including the chicken tacos provided as a demonstration.

"Later, you'll see a shift to beetles that consume the skin, hair, and cartilage [of a dead body]," Tomberlin said.

Scavengers such as raccoons, coyotes, and possums will also consume the remains. In the southern U.S. under the right conditions, "vultures can consume and skeletonize a human body in a matter of hours," said Tomberlin.

Colonization of the Dead

The forensic entomologist studies flies and maggots in his laboratory to figure out just what factors influence when the insects colonize human or animal remains.

"Time of colonization can vary from one decomposing body to the next," Tomberlin explained. A better understanding of colonization times would "allow forensic entomologists to better predict the actual time of death of the person in question."

Not much is known about what attracts insects to a decomposing body. Researchers suspect that the odors released by the microbes as they break down a body are a major factor in that attraction, Tomberlin said.

He is quick to point out that although the topic of dead bodies can be macabre, death and decomposition are natural processes that "play an important role in how an ecosystem operates.

"Nutrients are used to create a living animal, and when it dies the nutrients are returned to the environment," Tomberlin said. "Understanding that process is very important as it can apply to forensic science and human health."