Pheromone

Some living things send out secret smells.

These smells are like tiny messages. They help friends talk to each other.

Some smells say "Watch out!"

This tells others to run from danger. Other smells act like a map. They show where to find food.

Ants use these smells to make trails. This helps more ants find the way. Some smells help animals find a mate.

Even plants use these smells. A plant can send a message to its neighbors. This can help them stay safe.

Many different living things use these smells to work together.

Living things use special chemicals to talk. We call these pheromones. These chemicals act like tiny messages. They help animals and plants act in certain ways.

Some pheromones are for safety. An aphid might release a smell when a predator attacks. This tells other aphids to flee.

Some plants even send out smells when they are eaten. This helps nearby plants stay safe.

Other pheromones act like maps. Ants use them to make trails. These trails lead other ants to food. As long as there is food, ants keep making the trail. If the food runs out, they stop.

Some pheromones help animals find mates. A female silkworm lets out a chemical called bombykol. This attracts a mate.

Other animals use them to mark their homes. Dogs and cats use scent to show where they live.

Even tiny bacteria use these signals to work together.

Living things use special chemicals to send messages to others of their kind. These chemicals are called pheromones. A pheromone is a substance that an organism makes and releases into the world. When another member of the same species finds the scent, it triggers a response. This response can change how the animal acts or even how its body works.

Pheromones are used by many different living things. They are used by tiny bacteria and very large animals. They are also used by plants and insects. Scientists study these chemicals to understand how nature works.

There are many different ways these chemical messages work. Some pheromones act as a quick signal to change behavior. For example, an aphid might release a scent when a predator attacks it. This tells nearby aphids to run away.

Other pheromones act as a slow signal to change how a body develops. These are called primer pheromones. A mother rabbit releases a pheromone in her milk. This tells her babies to start nursing right away.

These different types help living things survive in many ways.

People have studied these chemical signals for a long time. Scientists like Jean-Henri Fabre and Karl von Frisch looked at how insects use them. Von Frisch called some of these signals "alarm substances." In 1959, Peter Karlson and Martin Lüscher created the word "pheromone." They made the word by joining two Greek words together. Earlier, a German scientist named Adolf Butenandt found a specific chemical called bombykol. This chemical is released by female silkworms to find a mate. This discovery helped scientists understand how chemical messengers work.

Many different groups of animals use these scents for specific jobs. Ants use trail pheromones to lead others to food. They must keep renewing these trails because the scent evaporates quickly. Some insects use aggregation pheromones to gather in large groups. This helps them find mates or defend against predators.

Even the pronghorn antelope uses scent to warn others of danger. An alarmed pronghorn releases a smell that reminds people of buttered popcorn. Humans can smell this scent from 20 to 30 meters away.

These chemical signals connect to many things you see in nature. You might see ants following a line on the ground. That line is often a pheromone trail.

You might also see a dog mark its territory. Dogs use pheromones in their urine to show where they live. Even in the ocean, sea urchins release chemicals into the water. This tells other urchins to release their cells at the same time. Pheromones are a huge part of how the natural world communicates.

A pheromone is a chemical substance secreted or excreted by an organism to trigger a social response in members of its own species. These chemical messengers are transported outside the body to affect the recipient. They can impact neurocircuits, including the autonomous nervous system. This can lead to physiological changes mediated by hormones or cytokines. It can also cause inflammatory signaling, immune system changes, or immediate behavioral shifts. Pheromones are used by a vast range of life, from unicellular prokaryotes to complex multicellular eukaryotes.

Scientists categorize pheromones based on how they affect the recipient. Releaser pheromones cause an immediate change in behavior. These often act as powerful attractants that can draw mates from over two miles away. Because they trigger rapid responses, they are typically quickly degraded. In contrast, primer pheromones have a slower onset and a longer duration. Instead of changing behavior, they trigger changes in developmental events. Maud Norris first described these primer pheromones in the species Schistocerca gregaria in 1954. There are also signal pheromones, which cause short-term changes like the release of neurotransmitters.

One major category is aggregation pheromones, which cause individuals to gather in one location. This group is called an aggregation. These chemicals help with mate choice, defense against predators, or overcoming host resistance through mass attacks. Many insect groups use them, including Coleoptera, Collembola, Diptera, Hemiptera, Dictyoptera, and Orthoptera. In recent decades, these have been used to manage pests like the boll weevil (Anthonomus grandis) and various weevils. Because they are effective at very low concentrations and are non-toxic, they are highly selective suppression methods.

Alarm pheromones serve as urgent warnings. Some species release volatile substances when attacked by a predator to trigger flight or aggression. For example, the milkweed aphid releases pheromones and sticky wax when attacked, causing nearby aphids to flee.

In bees, ants, and wasps, these chemicals can trigger aggression. The species Vespula squamosa uses them to alert others to threats. Even plants use them; some emit alarm pheromones when grazed upon. This causes neighboring plants to produce tannins, which makes them less appetizing to herbivores.

Trail pheromones are essential for social insects like ants. Ants use volatile hydrocarbons to mark paths to food sources. As long as the food is available, visiting ants continuously renew the trail because the pheromone evaporates quickly. If the food supply dwindles, the trail-making stops. Interestingly, Pharaoh ants (Monomorium pharaonis) use a repellent pheromone to mark trails that no longer lead to food. This helps the colony engage in more efficient collective exploration. Other species, like the army ant Eciton burchellii, use pheromones to maintain foraging paths.

Sex pheromones are vital for reproduction across many species. In animals, they often indicate that a female is available for breeding. Some insects, like certain moths and butterflies, can detect mates from great distances. At a microscopic level, bacteria like Bacillus subtilis release chemicals to induce a "competent" state in neighbors. This allows bacteria to take up DNA from other cells through a process called transformation. Even sea urchins use pheromones to coordinate the simultaneous ejection of sex cells into the water.

The history of pheromone research involves many notable scientists. The term "pheromone" was a portmanteau coined in 1959 by Peter Karlson and Martin Lüscher. They based the name on the Greek words for "to carry" and "apart." Earlier researchers included Jean-Henri Fabre and Karl von Frisch, who called them "alarm substances." A major breakthrough occurred when the German biochemist Adolf Butenandt characterized bombykol. This was the first well-characterized pheromone, released by female silkworms to attract mates. This discovery helped define how chemical signals elicit innate behaviors in conspecifics.

Pheromones also play roles in territory and social maintenance. Dogs and cats deposit territorial pheromones in urine to mark boundaries. In social seabirds, the preen gland is used to mark nests and territories. Other specialized signals include necromones, which are released by decomposing organisms. These allow crustaceans and hexapods to identify the presence of dead members of their species. There are even chemicals like TAA in rabbit milk that induce suckling behavior in newborns. This shows how chemical ecology connects to almost every aspect of biological survival.