Weaponized Fragrances: A Look At How Terpenes Are Used Throughout Nature

Wartime communication is among the most crucial and important communication, in terms of conveying a message without any room for misinterpretation. Throughout history, man has used smoke signals, lamps, flags, semaphores, morse code, musical instruments, even pigeons, to communicate a dire message quickly. We've made complex encrypted code sequences that evolve and morph as opposing forces to attempt to decode and understand these signals.

Believe it or not, terpenes are nature's version of these wordless wartime signals. Often the release of a terpene into the air can determine whether or not a plant lives or dies, or whether or not an insect gets to eat its lunch. All throughout the natural world, terpenes are used to attract and repel, to protect and defend, and to communicate both between species (intraspecific) and between organisms of different species (interspecific). Flowers give off terpenes which have scents that bees are drawn to. Insects and animals give off terpenes to attract mates or repulse those who would kill and eat them.

Plants emit very specific compounds for specific circumstances. Many different organisms are able to communicate with each other by means of chemical signals, or semiochemicals. Semiochemicals are chemicals which mediate interactions amongst organisms, either from different species (allelochemicals) or within the same species (pheromones). Humans and most other organisms have an olfactory system designed to perceive and discern thousands of different chemical compounds.

 Pheromones are compounds that elicit an unconscious reaction and can be classified into four major categories: alarm pheromones, sex pheromones, trail and aggregation pheromones.

ALARM

Alarm pheromones, aptly named, alarm neighboring organisms of incoming predators and impending danger to trigger a fight or flight response. Their the SOS of the plant and insect world. 

Adopted in Germany in 1905, the ‘SOS’ three letter message quickly became the internationally recognized message for distress. While it is often thought it means “save our ship”, it actually does not stand for anything. The three letter message is easy to remember, which is crucial during emergencies. SOS remained the official maritime distress signal until 1999 when the Global Maritime Distress Safety System was created. SOS is still recognized as a visual signal of distress. 

Fish and many social insects, such as ants, wasps, and bees, utilize this chemical compound to use as a form of coordinated colony defense. As the Paul Revere of pheromones, this one has helped preserve the existence and evolution of many different organisms, as a bee versus a bird is a lopsided altercation, but twenty bees versus one bird is a skirmish worth placing a bet on. A plant version of an alarm pheromone is the pleasing fragrance grass emits when cut. While you bask in the scent of summertime, the grass is trying to save itself and the rest of the uncut grass by releasing terpenes to act as a distress signal and ward off herbivores.  

SEX

Sex pheromones influence mate location and impact courtship behavior. Like humans, insects release and respond to sex pheromones which inspire an entire repertoire of sexual behavior. A male insect may be attracted to and attempt to copulate with an inanimate object that has sex pheromone on it.

Sexual pheromones in general are relatively understudied and underexplored but sexual pheromones released by humans are especially controversial and scientifically unproven. An interesting anecdote authored by Taryn Hillin in Splinter revolved around the commercialization of human sexual pheromones. The piece details the work of biologist Winifred Cutler, who in the late 1980’s, through a series of experiments, claims to have located and extracted the specific chemical compound that was responsible for human sexual pheromones. Cutler went on to patent the pheromone formula and has yet to disclose the mysterious chemical, as of this writing in 2021.

Her product promised to help women attract men, naming it the Athena Pheromone™. She soon began selling her “pheromone perfume” through the Athena Institute for Women’s Wellness in Pennsylvania, a biomedical research organization that she founded in the eighties. In 1995, she began selling a pheromone formula to help men attract women as well.

In one relatively famous study along the path to identifying the chemical, Cutler collected armpit secretions from both fertile men and women and froze the samples. A year later, she and her team thawed the secretions and placed them on the mustache region of a different set of subjects. The researchers found that the secretions increased the frequency of sociosexual behaviors such as kissing, petting, dating, and intercourse between subjects. Today, both varieties are available to order through the Athena Institute’s website, and both promise to “increase the romantic attention you get” from any partner.

However much skeptics may disagree, the “love serum” seems to work. In one study undertaken and published by the Archives of Sexual Behavior in 1998, in which Cutler was involved, 38 heterosexual men were studied. Men who wore the pheromones saw an increase in frequency of sexual intercourse and sleeping next to a romantic partner, as well as more instances of kissing, petting, affection, and informal dates.

A second study, published by Physiology and Behavior in 2001, which was conducted independently at San Francisco State University, focused on 36 women. It found that women who wore pheromones got more formal dates than women who did not. Researchers also found that 3 or more sociosexual behaviors increased over the baseline for 74 percent of pheromone users compared with 23 percent of placebo users. The increase in sociosexual behaviors included sexual intercourse, sleeping next to a romantic partner, and petting/kissing behaviors.

Whether or not this curious phenomenon is genuine, I haven’t a clue, but Cutler claims her formula contains a chemical copy of the human sex pheromone. Since it is technically a cosmetic, and not a drug, Athena Pheromone™ does not need assent from the FDA to sell the product commercially and the unknown serum could truly be anything.

TRAIL

Trail pheromones are used for marking pathways and signaling the location of food or resource richness. Fire ants depend upon trail pheromones in order to find food and bring it back to the nest. It’s this pheromone which explains the old cliché joke of a line of ants marching towards an innocent picnicker and stealing all of their food.

For many insects, these chemicals are their language. It’s how they communicate and how they prosper. The process of creating a trail begins with a scout ant finding food. After it has fed, it deposits a trail of chemicals as it returns to the nest. Inside the nest, it attracts other workers in a variety of ways that are not entirely understood. It may include antennal contact, regurgitation, jerking movements or the emission of another odor that recruits workers to leave the nest.  The insects then follow the trail of pheromones laid out by the scout and bring back as much delicious grub their little exoskeletons can carry.

AGGREGATION

Another major category of pheromones which are commonly extracted as terpenes are aggregation pheromones. They're called aggregation pheromones because when used by an insect, a considerable number of same-species insects will appear.  These chemical compounds function in mate selection but are used as a sort of back-up call when a large group of organisms are needed to overcome host resistance.

Aggregation pheromones are used widely across the world for pest suppression as they are nontoxic and effective at low concentrations. While other types of pheromones exist, these four are the most prominently extracted and used. Communication is absolutely vital for smaller insects and microorganisms to be able to thrive and continue evolving and these pheromones serve as an evolutionary tool as well as the precursor to terpenes. This ‘multilingual’ function of terpene further highlights their evolutionary benefit as they are one of the few substances recognized by nearly every living organism on the planet, prokaryote and eukaryote alike.

Discovering, identifying, extracting, and using these chemical compounds for our own human benefit is truly a remarkable human marvel and achievement attained through the intelligence and dedication of many brilliant scientists and botanists. Many plant scientists believe terpenes evolved to protect plants from pests by repelling them, killing them, trapping them in their sticky resin, and attracting predators to eat them.

We are able to extract these compounds and aromatic oils and to use them to benefit our lives in a vast amount of ways.  Terpenes have incredible power both in the mind and over basic bodily functions and the fact that they smell and taste wonderful is an evolutionary design enticing us to extract, smell, and ingest them. 

DEFENSE

Farmers have learned to tap into the chemical defense which plants already know and have been utilizing. For example, there are various pests that damage vital food crops such as corn and wheat. Borers, weevils, and other pests are known to quickly cause total crop destruction. Luckily, there are terpenoids like camphor, which demonstrated its power when applied to filter paper and offered to the wheat weevil, maize weevil, red flour beetle, and the larger grain borer. The isolate Camphor foiled the pests’ plans, repelling 80-100% of the bugs, and had the added ability to inhibit the development of eggs and other immature growth stages, providing a weapon against all stages of beetle and weevil life.  

Female red spider mites release the terpene nerolidol in the cocoon to use in a different form of defense. Male red spider mites heel to the scent of nerolidol (as well as geraniol and farnesol), which can be found in plants like corn and tomatoes, but also jasmine, magnolias, and cannabis. The male mite has been shown to emerge from hiding to dutifully watch over the female, who is about to emerge from her cocoon, all thanks terpenes emanating from within the cocoon.  

COMMUNICATION 

Communication is absolutely vital when predators or inclement conditions are afoot. When you can't shout, insects, plants, trees, and even animals will release terpenes as a form of wordless communication. 

Honeybees utilize geraniol as part of a cocktail of molecules collectively known as the Nasanov pheromone. Worker bees emit this pheromone to help navigate foraging bees back to their homes with the food.

Aphids release the terpene β-farnesene to sound the alarm that an attack is imminent, letting other aphids know to disperse. While β-farnesene might help keep aphids safe, it too has a dark side. The pine sawfly lays eggs on pine twigs, the process of which releases a volatile cocktail in which β-farnesene is the primary active ingredient. A parasitic wasp picks up the scent and flies to parasitize the eggs.

Plants communicate chemically as well, especially when they are being eaten. Their fragrant cries for help can signal eaters of herbivores to come to their rescue. Such is the case with lima bean plants. Evidence points to chemical communication through the air from one plant to neighboring plants cautioning to the presence of predators. Amazingly, some studies have found that plants responded to their neighbor’s aerial messages by bolstering their own chemical defenses. 

Honeybees communicate parent to child and amongst the adults using terpenes. So, terpenes interweave themselves throughout sentient nature, performing all sorts of tasks running the spectrum from aiding to annihilating. It’s some of the functions of terpenes in nature that I’d like to explore in this article. 

Another terpene that honeybees use to communicate is ocimene. Human babies cry when they want food, but honeybee larvae produce transβ-ocimene to express their hunger. The strongest concentrations of transβ-ocimene are emanated from the time just after the larvae have hatched to when they are three days old, illustrating the importance of the terpene exchange during fragile periods of growth 

Nature's Spice Cabinet

As shown, the weaponized wrath and utility that a plant can wield with its arsenal of terpenes is incredibly diverse and versatile. Winemakers like to say that “grape vines must suffer to make good wine.” Hot days and bitterly cold nights are stressful on the plant and create volatile compounds known as proanthocyanidins. These semiochemicals, like terpenes, are flavonoids which provide the flavor, and are much more expressed by the plant and abundant in presence when the plant is stressed.

All of this is to say, there is a direct relationship between the plant’s stress and our satisfaction. It's not always a 1:1 relationship, but the more the plant thinks it is going to die or the closer the plant actually comes to death, the stronger the scent, the more abundant the flavor, and the higher the concentration of terpenes. Thus, the more physiological benefit we receive from these plants. There’s poetic beauty in our relationship with these plants. It’s a yin yang. The greater the suffering in the plant, the greater the benefit we receive upon consumption. Terpene blends and isolates are more than just natural flavoring, they're compounds that were forged through generations of evolution, designed to have profound physiological effects on those who interact with them. 

For a list of effects certain terpene profiles have on us, click here. Otherwise, thanks for reading!

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