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Why Are Flies Attracted To Dead Bodies?

Updated: Apr 9

Why Are Flies Attracted To Dead Bodies GRAPHIC

It's always fascinating how quickly insects - especially flies - can detect and find a dead body. Long before the police and crime scene experts are even aware of a dead person, insects have already located and started hovering around the corpse.

Flies are attracted to dead bodies because of the smell and heat decomposing corpses emit. They, therefore, use the smell and heat to detect and locate a body in different stages of decomposition and settle there to lay eggs and assist in helping the body decompose.

Join us as we explore this fascinating phenomenon, learn how and why dead bodies attract flies, the various stages of decomposition, and what role flies play in the decomposition process.

Why Flies Are Attracted To Dead Bodies

Apart from feeding off the moisture and nutrients a corpse provides, female flies predominantly use a decaying body to lay their eggs.

Egg laying and hatching

A decomposing body provides the perfect temperature (especially in warmer climates), moisture, soft tissue, and nutrients on which newly hatched fly larvae can feed.

Flies possess a highly developed sense of smell that enables them to detect the distinct chemical compounds or odors released during the early stages of decomposition. These compounds attract the flies, guiding them to the source of decaying organic matter to lay their eggs.

A single female can lay up to 300 eggs on or within the corpse to ensure the survival of her offspring. The eggs hatch within a day, giving rise to larvae or maggots that feed on the decaying flesh, fluids, tissues, and blood, helping break down the carcass as they grow and develop.

After a few days of feeding and maturing, the blow, flesh, and house fly larvae leave the carcass to pupate in the soil, hatching after two weeks as adult flies.

Nutrient recycling in ecosystems

Flies also - unknowingly to them - help recycle nutrients within ecosystems.

When a person or animal dies, a complex ecosystem of decomposers, including bacteria, fungi, insects, and other organisms, work together to break down the organic matter, releasing essential nutrients like carbon, nitrogen, and phosphorus into the environment.

Fly larvae are also a rich source of nutrients for other insects and animals, helping recycle nutrients in an ecosystem.

The Smelling Abilities Of Flies

House, flesh, and blow flies, also known as carrion flies, have remarkable olfactory abilities, enabling them to detect specific odors associated with decaying organic matter, such as dead bodies, from miles away.

They have millions of tiny hairs on their antennae, which contain receptors for specific, distinct odors. These distinct odors, also known as volatile organic compounds (VOCs), attach themselves to the receptors on the fly's antennae, and a signal is sent to the insect's brain, alerting it to a food source and egg-laying location. They also use the heat emitted from the dead body to locate it.

Female blow, house, and flesh flies are specially adapted to pick up these specific odors and fly toward the source of the smell, where they feed off the moisture and nutrients of the dead body. They also use the opportunity to lay their eggs here, ensuring a habitable place for their offspring to hatch, feed, and develop.

Males are less interested in feeding and instead visit the decaying body to find females for mating.

Some flies are more attracted to dead bodies than others

Certain species of flies, also known as necrophagous or carrion flies, exhibit a strong affinity for decaying flesh. These flies include blow flies, flesh flies, and house flies - all playing an essential role in the decomposition process by laying eggs on carcasses.

Understanding The Decomposition Process

There are several stages of decomposition, each playing a pivotal role in why flies and other insects flock to, feed on, and inhabit a decaying corpse.

According to forensic entomology experts, decomposition happens in five major stages, during which several insects, microorganisms, and natural biological processes contribute to decay:

Stage 1: The fresh stage

This stage kicks in as soon as the person has taken their final breath and lasts until the onset of bloat. The corpse cools down, blood pools in the lower extremities, and rigor mortis sets in.

Though one may not see any significant changes externally, the body undergoes several chemical and biological processes internally. Bacteria start breaking down tissues in the gut, releasing enzymes that break down other cells, causing the body to release minute amounts of VOCs.

Insects detect the VOCs in the air, locate the body, and colonize it to consume nutrients and moisture. Other early colonizers, including female blow flies, house flies, and flesh flies, find natural cavities, such as the nose, mouth, or wounds, to lay eggs.

Stage 2: Bloat

The second stage of decomposition occurs when the body's internal environment has entirely run out of oxygen.

The anaerobic conditions form the perfect environment for microbial growth. These microbes produce gases like carbon dioxide, hydrogen sulfide, and methane, leading to the bloating of the dead body. The abdomen swells due to gas accumulation, while the corpse darkens and gives off a putrid smell, attracting more insects.

It's also during this stage that the fly eggs hatch and feed on the decaying corpse - after being deposited here by a female during the initial stage of decomposition. Other insects, such as carrion beetles, join the fly larvae to feed.

Stage 3: Active decay

During this stage, an estimated 24 to 72 hours after death, the body's tissues liquefy, and the abdomen deflates as gases escape through small holes created by the feeding insects.

Beetles become the secondary colonizers and dominant feeders. Rove beetles and clown beetles consume the live maggots filling the body cavities.

Stage 4: Advanced decay

Most of the soft tissue has now been consumed, and dermestid beetles arrive to feed on what remains - cartilage, hair, and dried skin - while the skeleton becomes visible.

Stage 5: Dry remains

In this final stage, marking the completion of the decomposition process, only the bones and some connective tissues remain. The skeleton is exposed, gradually bleaches in the sunlight, and is eventually scattered by animals.

Cleaning After Death

Under normal circumstances, a body stays in a mortuary where the colder temperatures in fridges help delay decay.

However, an undiscovered body, whether caused by homicide, suicide, or unattended death, may enter various stages of decomposition, requiring the affected area to be cleaned by specialized professionals, like Chore-ology.

Often referred to as the second responders, we have the necessary training and experience to clean and disinfect environments contaminated with human blood, bodily fluids, and other biohazards.

Cleaning after a death poses significant challenges, especially when dealing with the removal of blood or bodily fluids, which require meticulous attention to detail and adherence to strict safety protocols -something Chore-ology's team of professionals are highly skilled, trained, and certified at.

With unattended deaths, where a body remains undiscovered for an extended period, the decomposition process intensifies, leading to a potential fly and maggot infestation within the household.

Therefore, entrusting the professionals with the cleanup process ensures the removal of all organic material, the safe and secure decontamination of the affected area, and helps prevent maggot and fly infestations.

Contact Chore-ology today to learn about our range of biohazard decontamination and other household cleaning services.

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