What's this?

Who’s this? Wilbur the rove beetle, of course!

Last week we asked why this guy is such a big deal in pathology. Pakasuchus came very close in guessing – although Wilbur is alive and kicking, the body he lived in most certainly was not!

Wilbur and his bug buds are important to pathologists because they are the best way to figure out the time of death. The study of insects (and other arthropods) in decomposing remains is called forensic entomology. Wilbur is a rove beetle (Ocypus sp.), and eats maggots that infest dead bodies. Bugs ‘colonise’ bodies with a very particular timing and in a very specific order depending on the conditions around them, which forensic entomologists use to estimate the time since death.

The order can vary hugely, but generally the first wave of colonisation brings blow flies, attracted by the smell of blood, body waste, and general death odour, which lay their eggs on the body. These flies in turn attract further fly species (including the appetisingly-named ‘cheese flies’ and more conventional corpse flies), and along with decomposition, sets up the second wave of colonisation. The third wave, attracted by rancid fat, arrives, and now that the body is popular the more hipster members of the first wave get bored and move off.

Doesn't just eat cheese!

Doesn’t just eat cheese!

Eventually, Wilbur and his beetle buddies muscle in on the action. Some feed off the rotten juices, others tackle drying tissue (too tough for the flies), but Wilbur likes his meat fresh – other bugs are the plat du jour!

Wilbur's dinner!

Wilbur’s dinner!

Although most people are familiar with forensic entomology in human murder cases, it is also used to determine time of death in animal cruelty cases.

Bugs can also be a valuable source of other evidence too. Different creepy crawlies obviously live in different places, so can identify the geographic location of death. But they also have very specific local preferences too; some preferring sun, others shade, and even some indoors! They can tell you where the body was at the time of death, and where it has been since – useful for tracking the footprints of bad guys (and zombies).

They might tell you about the circumstances that an animal has come from. Certain flies are attracted to urine and faeces and their presence on a body suggests that the animal may have lived in a confined area surrounded by its own waste prior to death.

If the body has been in a fire, insects can survive safe inside the skull munching on grey matter,  telling you whether the animal died before or during the fire. If the latter, they will also tell you the time of the fire.

Usually different body tissues are sampled to test for the presence of drugs or poison, but if the body is too rotten or otherwise destroyed (e.g. burned), maggots can be tested instead! Having no arms or legs, maggots can’t hold on and frequently fall off the body. DNA can also be recovered from these maggots’ stomachs, to prove the body was in a certain place or in cases where it hasn’t been found.

Even no bugs at all is an entomological clue! Lack of insects on anything but a fresh corpse suggests that it has been frozen, kept in a tight container, or buried very deeply underground.

the more you know

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