Tahoe Deathfall

by Todd Borg

Street and I dropped Jennifer at the Tahoe Acad­emy in Zephyr Cove and then drove north up the lake. We went through the Cave Rock tunnel, headed up Spooner Summit. Spot dozed in the back seat.

  “Diamond said you took samples out at the crime scene yesterday?”

  “Yes. The word is finally getting out to law enforcement that entomologists should be brought in before the body is disturbed. So I did my thing while they took pictures of the body and the surrounding territory. I also set up a hygrothermograph so I can record temperatures and humidity over the next week. You want to see the site? They removed the body to the morgue after I was done.”

  “Sure.” I was impressed with Street’s sense of cool even though she’d been pulling insects out of a corpse just hours before.

  “Just continue over Spooner Summit and I’ll tell you when to turn off the highway. Do you think this body is connected to Jennifer’s sister in some way?”

  “No,” I said. “I wondered about the missing care­taker, but he’s been gone only eight or nine days. From what Diamond said, it sounded like the body is female and has been dead considerably longer.”

  “Yes. Large parts of the corpse were desiccated. Just skin and bones. The skull was completely cleaned. I found specimens in the abdomen where there was still some moist tissue. But most of the maggots had already left and there were numerous hide beetles making fast work of what was left of the body. The results won’t be very specific until I get the temperature records for the ravine where the body was found.”

  “Temperature affecting the bugs, right?” We’d crested the summit and started down toward the Carson Valley three thousand feet below.

  “Yes. It’s critical to the development of maggots and hence to the decomposition of the body. After I get several days worth of readings from the hygrothermo­graph, I’ll be able to compare them to the temperatures and humidity reported by the Weather Service. The difference in the monitor’s recordings and the Weather Service’s recordings will allow me to look back over the last few weeks and extrapolate what the temperatures and humidity were at the site where the body was found. Once I know that, I can establish an approximate time of death.”

  “You found numerous maggots in the body?” I asked, knowing that maggots were the primary target of Street’s forensic inquiries.

  “There were a fair number of maggots in the third instar stage. But they were already through feeding and were wandering away from the body to find a drier place to prepare for the pupal stage. Many of the maggots had already formed pupas on shrubs nearby.”

  “How long does that indicate since death?”

  “That is what I’ll know after I get the temperature data. Oh, the place where we turn off is coming up. See the giant boulder at the edge of the next big curve in the highway? You can pull in behind it. Then we hike from there. It’s about half a mile, maybe less.”

  I pulled off the highway and parked where Street indicated. There were lots of tire tracks, but all the sher­iff’s vehicles had left. We got out and Street led the way down an old Jeep trail. The pines were less dense than on the Tahoe side of the summit where moisture was more plentiful. It was easy to see through the forest. Unlike many foot trails, this Jeep trail was wide enough that Street and I could walk side by side. Spot bounded ahead.

  “If you were to guess about the time since death, what would that be?” I asked.

  Street gave me one of those looks that scientists must learn in school. A small tolerance for those who lack mental rigor.

  “I understand that it would be the most flagrant speculation,” I said. “And I swear never to tell anyone that you violated the sacred scientific principle of only speak­ing with benefit of facts.”

  Street’s look became withering.

  “Cross my heart,” I said.

  “Two and a half to three weeks,” she said. “And that’s only because it has been warm recently.”

  “How warm must it be for maggots to do their thing?”

  “The ideal from a maggot’s perspective is eighty degrees Fahrenheit. Any cooler than fifty degrees and they stop all activity. Warmer than ninety-five and they lose most of their liveliness, although they don’t die until one hundred twenty degrees or so.”

  “So, when it gets down into the forties or thirties at night in Tahoe, they would stop their activity?”

  “If they were outside the body, that would be true. But inside the corpse they are insulated from the night­time cold. Further, they generate their own heat.”

  “But insects are cold blooded.”

  “Yes. But their metabolism creates heat nonethe­less. And the heat of a maggot mass is substantial. The night temperatures could drop to below freezing, yet the temperature of a maggot mass could be as much as seventy degrees warmer.” Street pointed ahead to a fork in the trail. “We turn left up here.”

  “What, exactly, does the maggot mass do?” I asked.

  “Eat. A maggot is a highly specialized feeding machine. They use enzymes to begin the breakdown of the tissue before they actually consume it. Their com­bined heat helps speed the process and they are a critically important part of the decomposition of a body.”

  “A lovely picture,” I said. “After the flies lay their eggs, how do the maggots get inside the body?”

  “The female blow fly, flesh fly and house fly all have an uncanny ability to find the natural body openings and they lay their eggs at those spots. In the case of this body, the flies would have also laid their eggs near the bul­let holes in the head. When the eggs hatch after a day or so, the tiny first instar maggots have an equal talent for burrowing into those openings where they start eating the moist flesh.”

  “How long does this go on?”

  “It only takes a day or so for the maggot to out­grow its skin. They molt, and the second instar begins.”

  “You can tell these apart.”

  “There is a size difference between the different instars,” Street said. “But to be certain, you have to look at the posterior spiracles. Those are the breathing structures of the maggot.”

  “Of course,” I said.

  “Another day, another molting, and the third instar emerges. This guy feeds voraciously for one to four days, then leaves the corpse to find a safe place to begin pupation.”

  “That’s like a cocoon?”

  “Yeah. The pupa looks like a little football. And from that, in a week or so, emerges our glorious little fly.”

  “How long does the whole process take?”

  “Ten to twenty-seven days from egg to adult fly.”

  “Depending on temperature,” I said.

  “And species and moisture and position of the corpse and the presence of social insects...”

  “Wait. What does position of the corpse have to do with it?”

  “A corpse that is buried or even wrapped in a blan­ket slows down the process. It is harder for the flies to gain access to lay eggs among other things. A corpse that is hanging is difficult for beetles to get to. They come after the maggots and do the final cleanup, so to speak.”

  “You mentioned social insects.”

  “Right. The necrophagous species like maggots feed directly on the corpse and accelerate decomposition. But there are predators and parasites of those species, espe­cially among the social insects.”

  “You mean wasps eat maggots?”

  “Wasps both predate on flies and parasitize mag­gots. Some wasps lay their eggs directly on the maggots. When those larva hatch they feed on the maggots even as the maggots are feeding on the corpse. Then, of course, there are the ants, many of which eat maggots. The ants of a large colony can carry off maggots in great numbers, substantially slowing the effects of the maggots on the decomposition of the body.” Street stopped hiking and looked around. She walked to the side of a clearing and looked through a stand of trees. “Over here, Owen.”

  I walked over and looked where she was pointing.

  “The corpse was under that tree,” s
he said.

  THIRTEEN