Before heading into the field last week, each detective claimed a token — a small vial filled with alcohol and a single floating blowfly larva.

The preserved “pet maggots” were to remind the Hammond police officers that these insects can speak for the dead.

The police then trekked out to the Southeastern Louisiana University outdoor education laboratory where live bugs were waiting to be collected and studied. Different species and stages of life can help establish a timeline for murder, as well as provide other insights into a crime.

It was Thursday just before noon. Three-and-a-half days earlier, SELU biology Professor Erin Watson Horzelski took a dead beaver out to the wooded site and left it there. Normally the forensic entomologist would use a pig carcass, but her pig carcass guy couldn’t make a delivery in time, so a spare beaver at the biology department was thawed out to fill in. Humans, pigs, beavers — the maggots aren’t picky.

By the time the officers arrived, the creature’s orifices were teeming with life, and larvae wriggled excitedly behind its orange buck teeth.

Several detectives were less than pleased with the sight — and the stench. While a few grabbed plastic spoons and bug nets and set to work, others had to be gently coerced.

There were taunts among officers that the reluctant ones better get used to the smell, since they’d be picnicking at the lab for lunch, and at least one instance of a sergeant surreptitiously tickling the back of a detective’s ear to suggest the flies had moved on to fresher meat.

Before long, most of the detectives dug in. In shallow bowls they sifted through dirt and leaves for larvae as if panning for gold. After acclimating to the smell, Hammond police Detective Chase Zaffuto showed off his captured beetle, describing it as a predatory species that feeds on the flies that are drawn to the carcass.

The beetles, blowflies and other insect scavengers help detectives and prosecutors piece together the chain of events that led to a death. Insects go through distinct periods of growth from eggs to larvae to pupae to adults, so finding them can help place a time of death or exposure.

Horzelski recalled one Tennessee case she investigated in which a defendant claimed he killed two people in a fit of passion after discovering they had slain a third man. However, the bugs told a different story.

The insects discovered on one victim’s body were older than the other’s. That suggested that the two people did not die in the midst of a single fit of rage, but that at least one of the killings was premeditated, qualifying the shooter for the death penalty, which he received.

In another investigation, police found a large mass of insects in an outdoor area away from where a body was found, indicating that someone had tried to move or conceal the corpse, the professor said. Insect growth is also affected by heat and light, and different species have different habitats, all of which can provide further clues for detectives.

“(Forensic entomology) is very valuable,” said Sgt. Gary Baham, a field supervisor for the Tangipahoa Sheriff’s Office, one of two members of parish law enforcement that joined the dozen city police in training.

The evidence isn’t just for murder, either. Baham and Horzelski said it can be useful in cases of abuse involving elderly, juvenile or disabled victims, or in investigations where a body has been dumped after an overdose.

The Tangipahoa Sheriff’s Office studied insects after recently discovering the body of a missing Ponchatoula man, Baham said. The deceased is believed to have died from a drug overdose, and two people have been arrested for negligent homicide.

Generally, experts like Horzelski can arrive on-scene to collect evidence, Baham said. But when they aren’t immediately available, it falls to police and crime scene specialists to know what to collect and how to preserve the small, often living, evidence.

Flies can go right in the freezer, but maggots and other “soft and squishy” creatures are often preserved in ethyl alcohol — though Everclear can do in a pinch, Horzelski said.

Some eggs and larvae may need to stay alive long enough to be studied by a professional, which means they need to be fed. The entomologist recalled one resourceful police officer who didn’t have quick access to a grocery store and showed up at the nearest Wendy’s for raw hamburger meat to keep his evidence alive.

But the bugs are worth the trouble.

“Witnesses are flippant,” Horzelski said. And evidence from bodies themselves can be tough to sort out, since left in the Louisiana heat, “eight, nine, 10 days, I’m gonna be gooey.”

Maggots and beetles tell the truth.

“They do matter,” the professor said. “You never know which one it is that’s gonna matter.”