Insect Witness

The investigation into the murder of Ma Rong had just been completed, and on July 18, a phone call came from the City of Lai saying that a citizen had found the body of a middle-aged man in an undeveloped hill north-east of Zeren Park, on the northern outskirts of Lai City. There was an unplanned growth of low trees scattered along the hillside, less than a kilometer from the highway to Hengyang in Lai City.

In the course of his search, he noticed first a small mound of sod, loosely covered with pine branches, crawling with rolling fat white maggots, the larvae of flies laying eggs on the carcasses of animals. He pushed aside the branches and found the body of a man. The dead man was dressed in a yellow and white uniform, his trousers hanging loosely over his legs, a white towel for wiping sweat on his head, and a third-class medallion of meritorious service hanging from his chest. He was lying on his back with his belt tied in two knots around his neck, and the other end of the belt was tied to a not very thick, broken branch. The maggots under the clothes occupied most of the bodies, and most of the flesh had already been eaten away.

Ding Wei, Liu Zhiwei, and Shen Yuan immediately rushed to the scene.

How long had the dead been there? Or, to be more precise, how long had he been dead? It was too late to judge by the temperature of the body, the rigor mortis had already occurred and had been resolved long ago, and the body was rotting little by little.

Liu Zhiwei estimated the deceased's death to be five to six weeks.

Shen Yuan disagrees, telling Liu that "he has been dead for at least 9 to 10 days, but probably no more than 12 days. The reason why the corpses became like this is entirely because of the maggots nibbling away at them. "

Liu Zhiwei suspiciously stared at Shen Yuan and said, "Strange, do maggots eat this meat so quickly?"

Shen Yuan said, "I've seen a corpse that became like this 10 days ago."

"Why is this happening?"

"Different insects have different properties." Shen Yuan said, "The maggots we see now are essentially the larvae of a blue fly. From the naked eye, the larvae of these flies are not different from those of other flies, but they hatch at different times. I should have kept these specimens at once. "

Shen's toolbox includes a collapsible net bag for catching flies, a magnifying glass, a digital thermometer, a digital recorder that records ambient temperature at regular intervals, and a wooden rice spoon. Shen Yuan explained that using this spoon to scoop up flies was very convenient. Some bugs were killed at the scene with boiling water and stored in ethanol for future analysis; others were sent to the culture room for culture at the right temperature. Shen Yuan needs to provide more information about the corpse's origin based on them. Shen Yuan introduced the fly to the police in Lai City: "After a very short period of time, the fly will come out of the corpse as a maggot. In the warm and fresh air, the number of maggots hatched at the same time can be so much that it can form a layer of maggots blanket, and it won't take long for the corpse to be bitten into pieces. "

"Is there any basis for your nine days of death?" Liu Zhiwei asked curiously.

"The life history of this green fly is very simple. It usually lays its eggs in the sun during the day, and when the weather is warm, larvae hatch on the first day. The young 'first instar larvae' molt after 8 to 14 hours and then 'second instar larvae' after 2 to 3 days. The third instar larvae, or fisherman's maggots, become pupae after devouring them for 5 to 6 days. The larvae we see now on the corpse are mature, old, fat, lazy, three-year-old larvae, not yet in the pupate stage. Plus, it will take some time for the flies to reach the body, so I estimate that the flies' eggs were laid nine to ten days ago, and that the time of death would be May 8 or May 9. "

From the way the dead man was dressed and the medals he wore, Ding Wei immediately knew who it was.

Lai City police called Qi Menglu, the corpse confirmed by Qi Menglu confirmed that the deceased is Chen Ai-cai. When she identified the body, she had fainted several times. If the smell on the corpse had not stopped her, she might have hugged the body and cried, but her voice had become hoarse in the end.

"Big brother, you have to help me find the culprit! I want to know who killed him!" Qi Menglu knelt down in front of Ding Wei once again.

Ding Wei's face turned pale as he looked at the extremely weak Qi Meng Dew. The death of Chen Aiki had given him a sense of foreboding, but right now he could not speak to Qi Menglu, even to question him about some of the things he really wanted to know about Chen Aiki before she died.

With the permission of Qi Menglu, the body was immediately taken to the Forensic Medicine Department of Nanhua University Medical School, not far from Lai City, for autopsy.

During the examination of the insect species, Shen Yuan found that the third instar fly maggots were seriously infected in the thyroid gland of the corpse. Among these maggots, Shen Yuan found two special flies, called horse carrion flies. It takes 28 days for a horse rot fly to develop from an egg to an adult at 16 ℃. The two pupae were reared at 17 ℃ -20 ℃ for 18 days. This was in line with his estimate of the time of death with the green flies at the scene.

The larvae of horse carrion flies feed on the dead before or after they lose consciousness and are often associated with the history of some major disease. In order to determine whether the deceased suffered from serious disease, Shen Yuan crushed the pupa and did biochemical test. The results showed that there was a tumor metabolite in the insect. A large number of squamous cell tumor lesions were found on the neck section. In addition to the presence of cancer tissue in the neck, the deceased was also found to have severe malnutrition.

Pathological examination showed that the tumor did not metastasize to other tissues, including viscera. The autopsy found a certain amount of sleeping pills in the stomach, but not fatal. There were numerous maggots on the corpse's neck. Shen Yuan speculated that the wound was where the belt was tied, and tentatively concluded that the victim had died from choking.

Since the body was highly decayed and had a large number of maggots, Liu first examined the exposed part of the head, neck and hands at the autopsy. While examining the neck, Liu Zhiwei saw a small puddle of dried blood clotting on the left side of the corpse's throat. Other than that, there were no other wounds. This was the only bleeding point in his body. The small bones on the same side of the larynx were not crushed. Shen Yuan speculated that the reason for the bleeding was that the left side of the victim's neck had been cut by thorns on the leaves.

"Your corpse has been heavily eroded to this extent. You actually said that the time of death was only around 10 days? I think your calculations this time are clearly wrong." At the time of the autopsy, Liu Zhiwei was still suspicious of the results of the insect calculation.

"Based on the insect phenomena observed during the examination of the body in the forest and my subsequent identification of the development time of the horse carrion flies, I stick to my original theory — nine or ten days after death. From the corpse's appearance, it can be seen that apart from the cyan flies, there is no other special situation that can accelerate the erosion of the maggots and the decomposition of the corpse. "

"I think Chen Aiki died at least a month after we found the body. Besides, it was all his doing. After the murderer strangled the victim with his hands, he used his belt to tie two knots around the victim's neck, creating the illusion of suicide. "

The two of them once again began to argue.

The Public Prosecutor of Lai City decided to assign a good pathologist and an entomologist to the provincial police, together with Liu Zhiwei and Shen Yuan, to clarify some points of doubt in the case. And asked the Lai city police to investigate all relatives and friends of Chen Aisui.

The entomologists sent by Shen Yuan checked the maggots he found at the scene and confirmed that they were the real larvae of the red-headed blue fly. At the same time, they praised Shen Yuan for recognizing the species of stables and carrion flies.

As clearly and briefly as possible, Shen Yuan introduced these fat third instar larvae, which had yet to pupate, as well as the three stages from egg to hatching and the development of maggots before pupation.

"With all these time added together," Shen Yuan said, "On the issue of time, I have no doubt that the deceased have been dead for about 10 days, or at least 9 days."