Part 39 (1/2)
”Very good. They're usually the first to emerge as adults. It takes them anywhere from sixteen to twenty-four days to mature, given temperatures around eighty degrees Fahrenheit. They'd be slowed under the conditions you describe.”
”Yes. It wasn't that warm.”
”But the empty puparial casings mean some of the flesh flies had finished their development.”
”Flown the pupae, as it were.”
”It takes the blowfly about fourteen to twenty-five days to mature, probably longer in the wet environment on your island.”
”Those estimates tally.”
”You also collected what I'm pretty sure are Muscidae Muscidae larvae, maggots of the housefly and its relatives. Typically these species don't show up for five to seven days after death. They prefer to wait for what we call the late fresh or early bloat stages. Oh, and there were cheese skippers.” larvae, maggots of the housefly and its relatives. Typically these species don't show up for five to seven days after death. They prefer to wait for what we call the late fresh or early bloat stages. Oh, and there were cheese skippers.”
Cheese skippers are maggots that jump. Though not always easy, I've learned to ignore them while working on putrefied bodies.
”My personal favorites.”
”Everybody's got to make a living, Dr. Brennan.”
”I suppose one has to admire an organism that can jump ninety times its body length.”
”Have you measured?”
”It's an estimate.”
”A particularly useful critter for estimating PMI is the black soldier fly. They don't usually show up until twenty days after death, and they're fairly consistent, even with buried remains.”
”They were present?”
”Yes.”
”What else?”
”The beetle a.s.semblage was more limited, probably due to the wet habitat. But the typical predator forms were there, no doubt munching happily on the maggots and soft-bodied forms.”
”So what's your estimate?”
”I'd say we're talking about three to four weeks.”
”Both bodies?”
”You measured four feet to the bottom of the pit, three feet to the top of the lower body. We've already discussed the preburial larviposition by the flesh flies, so that explains the puparial cases you found on and above the deeper body. Some held adults, half in and half out. They must have been trapped by the soil while trying to exit. The Piophilidae Piophilidae were there, also.” were there, also.”
”Lou?”
”Cheese skippers. I also found some coffin flies in the soil sample you took from above the lower body, and some larvae on the body itself. These species are known to burrow down to corpses to deposit their eggs. The soil disturbance in the grave and the presence of the upper body would have facilitated their access. I forgot to mention I found coffin flies on the upper body.”
”Were the soil samples useful?”
”Very. You don't want to hear about all the critters that chow down on maggots and decompositional materials, but I found one form that's helpful with PMI. When I processed the soil I collected a number of mites which support a minimum time since death of three weeks.”
”So you're saying three to four weeks for both bodies.”
”That's my preliminary estimate.”
”This is very helpful, Lou. You guys amaze me.”
”Does all this square with the condition of the remains?”
”Perfectly.”
”There's one other thing I want to mention.”
What he told me next sent an icy wind rocketing through my soul.
24.
”I'M SORRY, LOU. GO OVER THAT AGAIN.” LOU. GO OVER THAT AGAIN.”
”It's not new. The increase in drug-related deaths in recent years has prompted research into testing for pharmaceuticals in carrion-feeding insects. I don't have to tell you that bodies aren't always found right away, so investigators may not have the specimens they need for tox a.n.a.lysis. You know, blood, urine, or organ tissues.”
”So you test for drugs in maggots?”
”You can, but we've had better luck with the puparial casings. Probably because of the longer feeding time compared to the larvae. We've also played with beetle exuviae and fra.s.s . . .”
”Which is?”
”Cast-off beetle skins and fecal matter. We're finding the highest drug levels in the fly puparia, though. That probably reflects feeding preference. While beetles prefer dried integument, flies go for soft tissues. That's where drug concentrations are likely to be greatest.”
”What's been found?”
”The list is pretty long. Cocaine, heroin, methamphetamine, amitriptyline, nortriptyline. Most recently we've been working with 3,4-methylenedioxymethamphetamine.”
”Street name?”
”Ecstasy is the most common one.”
”And you're finding these substances in puparial casings?”
”We've isolated both the parent drugs and their metabolites.”
”How?”
”The extraction method is similar to that used on regular pathology samples, except that you have to break down the tough chitin/protein matrix in the insect puparia and exuviae so the toxins can be released. You do that by crus.h.i.+ng the casings, then using either a strong acid or base treatment. After that, and a pH adjustment, you just use routine drug-screening techniques. We do a base extraction followed by liquid chromatography and ma.s.s spectrometry. The ion breakdown indicates what's in your sample and how much.”
I swallowed.