An Understanding Of The Chemistry Of Pheromones Biology Essay


What are pheromones? ;A chemical secreted by an animal, usually associated with insects, which influences the behavior, physiology or development of others of the same species, often functioning as an attractant of the opposite sex.

The word "pheromone" is derived from the Greek "pherein", which means to carry, and hormon, which means to excite. Thus, pheromones can be described as an inter-body hormone, or a chemical that transmits a message between bodies. These messages are detected by other individuals which may or may not be of the same species, and usually signal something (be it fear, aggression, sexual arousal or many others) to those individuals. The effects of the detection of this signal carried by thepheromone or pheromones are varied and could range from sexual excitement to avoiding contact with an individual who is sending the signal. A more specific example of this is the reported altering of the phase of the menstrual cycle of women who live in close proximity, which has been linked to certain pheromones.

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In mammals there are three groups of pheromones:

Releaser pheromones that "release", or cause, an almost immediate change in behavior. Examples of this include attraction and aggression.

Primer pheromones have affects that are more long term, for example the altering of the phase of menstrual cycle in women.

Information pheromones carry information about an individual. This might include fitness, immune system type (Major Histocompatibility Complex genes), etc.

Generally, the pheromones in pheromone products are hormone related. For example, androstenone, androstenol and androsterone are all androstenes, and generally signify factors involved with sex. Copulins, a group of pheromones only produced by women, are mostly acids and organic acids.

It is also interesting to note that pheromones are not necessarily species specific. For example, out of androstenone, androstenol and androsterone, only androsterone is uniquely human pheromone.

How pheromones are produced:-

In humans pheromones are secreted onto our skin through the apocrine glands (sometimes called human scent glands). These are similar to eccrine glands where our salty sweat comes from, but the apocrine glands secrete a more oily substance. The apocrine glands are normally associated with hairy areas such as arm pits and the crotch area, and are also usually accompanied by eccrine glands which help to disperse the pheromone secretions. Apocrine glands are activated at puberty, along with hair growth in the axillary (arm pit) regions and crotch which increase the surface area for pheromone dispersal. Certain pheromones are directly related to masculinizing or feminizing hormones (testosterone or estrogens), and so high levels of these hormones will cause high levels of the related pheromones to be released.

Pheromones evolved because metabolic waste (hormones, short peptide chains, fats, sugars, etc.) that was secreted onto an animal's skin can give certain information about the internal chemistry and health of that individual. Over time species adapted to this fact giving rise to the whole pheromone chemical communication system. Modern animal and insect species have a somewhat more specialized pheromone system, where secretory glands and receptor systems have evolved.

Bacterial action may also have some role to play in pheromone production, but not much is known about this at the time of writing. For example, the pheromoneandrostenol may oxidise (by bacterial action) to androstenone. Androstadienone can also be converted into androstenone. However, bacteria are responsible for causing the bad smells associated with body odor, and they do this by metabolising the chemicals (including the pheromones) in the oily apocrine secretions. A study on bacterial action on pheromones can be found here.

Copulins are created in a different way to the "hormonal" pheromones. They are secreted into the vagina along with the bodies natural lubricant in redinness for sex.

How pheromones are sensed and processed:-

Pheromones fall under a category of chemical sensing (chemosensing for short) that is very similar to the way we smell. Our regular sense of smell (which is what you are using when you are smelling flowers) is called olfaction, but pheromones are thought to be detected and processed through an accessory olfactory system. In mammals this is the Vomeronasal System. This consists of vomeronasal pits situated somewhere in the nose, at the bottom of which lies the Vomeronasal Organ (VNO), which is where cells specialized for detecting pheromones lie. From here signals are sent by neurons (nerves) to the accessory olfactory bulbs, which is the part of the brain responsible for processing the information relayed by the pheromones and mediating a response. Most pheromone signals will end up at the hypothalamus. Interestingly, the epithelium of sensory cells in the nose is sometimes referred to as an extension of the brain because of their location and the way the signals are processed.

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In humans, this picture of pheromone sensing becomes more complicated with some scientific studies casting some doubt over the existence of a VNO in humans, which it was thought would rule out the possibility of human pheromones having any effect on other individuals. There was also some doubt over the existence of the appropriate genes that would code for the pheromone receptor proteins in the receptor cells, making it even more likely that the pheromones being secreted onto our skin would be redundant. With this and the thoughts that our VNOs are vestigial, we are left with a situation where the whole pheromone system as an evolutionary relic akin to the appendix. Some suggest that this is due to the evolution of tri-colour vision, which led to an evolutionary trade off. However (and there had to be a "however", or I wouldn't be writing this!), anecdotal evidence from pheromone users has always contradicted the science in this regard, but only relatively recently has the science started to catch up with the anecdotal evidence.

First of all, (aside for anything concrete about the vestigality of the VNO in humans) there is no evidence that the VNO is actually required for pheromones to be detected, and current knowledge and speculation is leaning towards the idea that VNO is not the crucial pheromone sensing organ it was once thought to be, at least to the point of having the pheromone detection load shared with the generic olfactory membranes (click here for relevant study). There has also been significant evidence for the detection of pheromones having an impact on brain activity of specific areas of the brain (click here for relevant study), which has actually shown that the presence of that particular pheromone affects activity in parts of the brain linked with social cognition and attention. Incidently, while our organs of chemosensing in general have reduced in size, the areas of the brain associated with the processing of these signals have actualy grown in size compared to other areas. There is also evidence (click here for relevant study) that pheromones affect the release of Luteinizing Hormone which itself is responsible for causing temporary spikes in the release of sex hormones (specifically testosterone), which can happen during attraction and arousal.

Interestingly, the most abundant pheromone on the market is androstenone, but this pheromone has been shown to have no action in the VNO. The only male pheromone on the market that has shown to have an effect on the VNO is androstadienone, which is a less well known male pheromone. We are therefore left with two categories of pheromone, compounds that activate the VNO and those that don't. The first type can be subcategorised into a group called vomeropherins, but normally all of the compounds are just labeled "pheromones".

Contrary to popular belief, pheromones do have a perceivable odor that we can detect through normal olfactory pathways. This smell is mostly identified as an acrid bad body odor smell, but some pheromones have a more pleasant smell and some have been described as the scent of fresh sweat, in a good way. However, these smells are only detectable at high concentrations. The "pheromones are completely odorless" myth arose due to the fact that some of the action of pheromones which causes reactions in other people is subconscious, and the pheromones can be present in levels far lower than their detection thresholds for generic olfaction to have an affect. This means that pheromones do not have to be smelt to work. There are also those who can not actually smell androstenone (about 25% of the male population), although studies suggest that people's noses can learn to smell androstenone (relevent study).

The affects of pheromones on behavior gets even more complicated in humans because we have evolved higher processing (consciousness) which can override, contradict or otherwise alter the affects our basic instincts have on our behavior. Take, for example, a situation where a guy is in a deeply committed relationship and is exposed to a very attractive signature of female pheromones. Here, higher processing would at the very least (assuming a high level of integrity on the guy's behalf) cause the attraction to be ignored, and at the most could cause the guy not to notice the woman at all. Behavioral reactions to pheromones have another added layer of complexity due to the nature of attraction and courtship in humans, with factors such as social status (think about levels of "attainability" here) and shyness playing their part to inhibit pheromone influences, but there are other factors such as a persons tendency to be sexually aggressive or just aggressive in general that can amplify the normal pheromone effects. A persons mood prior to sensing the pheromones can also play a role. All of these factors are intensified with the use of exogenous (i.e. from a bottle) pheromones.

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Is Primal Instinct your best product?

Primal clearly has a high concentration of androstenone, but there are other factors that sometimes make other products a better choice. Every product sold at has its loyal followers. Actually, the price of Primal is due to the extremely high pheromone content. You don't need that much at any one time. The manufacturer recommends only 2 drops per application, so a 10ml bottle lasts a LONG time. It is not any more effective than say NPA (male formula), which includes the same TYPE ofpheromone in it. It just lasts a very long time, since you only need to use 2 drops per application.

How do I make the most of pheromones?

Men: Be the "good guy"! Pheromones give you an aura of power, but that can be scary for shy women if you look grumpy or like a "lone wolf". Always look for opportunities to be helpful and supportive of women. It is also very important to be a friendly, interesting, entertaining guy. Pheromones will enhance these good attributes, but if they aren't there in the first place, there is nothing to enhance. 

Women: Be approachable! If you suffer from the "ice maiden" syndrome, pheromones are only going to push you further out of reach, even to guys you would love to get to know. You don't necessarily have to make the first move, but be ready to come up with a warm smile and maybe even a cheerful "hello" if you happen to make eye contact with a guy.

Human pheromones - An introduction

The first pheromone was identified in 1953. This pheromone, called bombykol, is secreted by female moths and carried a "come to me" signal to males. This signal can travel large distances and is effective at low concentrations.

The mammalian pheromone system was more difficult to understand because mammals, far from having the simple stereotyped behaviour of insects, have complex and independent behaviour. Mammals were found to detect pheromones through an organ in the nose called the VNO, which is similar in function to the olfactory membranes but connects to the hypothalamus.

Scientists were beginning to speculate whether a pheromone system existed in humans. In the 70's Martha McClintock noticed that females living in close proximity underwent a changing of phase of their menstrual cycles causing them to ovulate at similar times. It was discovered that this effect was due to a chemosignal, or pheromone. In 1974 Dr George Dodd descovered the first human sex pheromone, alpha-androstenol.

Although humans are mammals, it is not certain that all pheromones are detected by the human VNO; some may be detected by the olfactory membranes (by normal smelling). It is known that pheromones do not need to actually be smelled to exert their subconscious effect, although human pheromones that are commercially available do have a detectable scent at high concentrations. However, not all people are actually able to detect the conscious odour of pheromones, but apparently this does not reduce their subconscious effect.

Although commercially available human pheromones address a quite specific area of human interaction, attraction, pheromones play a role in other areas such as mother-infant bonding. Pheromone products are also from a specific family of pheromones which are derived from sex hormones which indicate youth, fertility, etc. Everybody secretes these chemicals, but not in the same quantities. Other pheromones are unique to the individual, such as the pheromones that signal tissue type (Major Histo-compatibility - the "T-shirt study"). The hormone derived pheromones are naturally secreted onto the skin via the apocrine glands, which are primarily situated in the arm pits and the pubic region; the hair in these areas helps to disperse the pheromones effectively. These scent glands have in some cases evolved to perform an entirely different and specialised role, for example in the ear to produce ear wax, or in women's breasts to produce milk.

It is known that androstenol can induce a spike in Luteinizing Hormone in both sexes, and this leads to a spike in testosterone levels which may be responcible for feelings of attraction.

Pheromone products usually contain these three pheromones:

Androstenone (a.k.a -none, Anone): Signals dominance and aggression, quite competitive. -none is often associated with a sexual response, but by no means exclusively.

Androstenol (a.k.a -nol, Anol): Signals youth, and sociability, often induces lots of talking, friendliness and comfort. As it often seems to cause conversation, it can be a good ice breaker.

Androsterone (a.k.a -rone, Arone): Signals masculinity. It also creates an impression of reliability and protection (i.e. "this is the alpha male who can look after me").

Copulins (a.k.a cops): Secreted in women's vaginas during ovulation, these are a collection of fatty acids and other biological molecules that serve to induce copulation. It is said that if a man smells Copulins on a woman, she is judged to be more attractive.

These are the most common three, but there are other types of human pheromones.

Human Pheromones and Face Preferences:-

Biometric Evidence that Sexual Selection Has Shaped the Hominin Face begs the question of what stimuli are most important to sexual selection across species. Human preferences for visually perceived facial and other physical features appear to have evolved via their association with olfactory/pheromonal cues (e.g., human pheromones). The evolved neurophysiological mechanism that links human pheromones to food choice and mate choice can be traced back to single celled organisms. In contrast, no known mechanism allows visual input to influence sexual selection in other species. Obviously, other species rely first and foremost on olfactory/pheromonal cues. Sexual selection must start somewhere for it to shape face preferencesheromones.

Are humans visual creatures?

People think that their first response to a physically attractive potential partner is due to visual input. That's not accurate! If we were not already conditioned by human pheromones to respond to physical attributes, we could not develop an appropriate response to what we see.

Perhaps it's easier to grasp this concept of odors and pheromones if you think about your food preferences. No matter how good it looks, if the odor isn't right, you're not going to be interested in the food. And no matter how good someone looks, you're not going to be interested in them if their scent signature is not right.

Even when the chemicals were transferred to you in the womb, your experience with food chemistry before birth set the stage for your adult food preferences. Just as food odors cause changes in our physiology that are associated with hunger, ingestion, and satiety, human pheromones cause our physiology to change. With the human pheromone-induced changes in physiology come human pheromone-induced changes in behavior. The changes in physiology and behavior happen without thought; you don't know that the changes are happening.

It's even more difficult to comprehend how thoroughly human pheromones affect our behavior because we are not aware of their affects. We think about what we see, and -- without thought -- attribute attractive physical characteristics to our visual perception. In truth, however, we are very much like other animals. We know that they depend on their sense of smell for food choice and for mate choice. We are like other animals that don't need to think about their choices. Neither do we --except that sometimes after-the-fact we may ask ourselves "What was I thinking?"

Pictures of food are visually appealing due to associations we make with the chemical appeal of the food. It wouldn't look good if it didn't smell good.

Pictures of people are visually appealing due to unconscious associations we make with their chemical appeal.  

Pheromones are chemical signals from other people that condition you to respond to what you see.

For example: which of these pictures do you find most attractive

These pictures are of a face that has been altered in appearance to show the difference between how high levels of testosterone change facial features (left) compared to how high levels of estrogen change facial features (right). The three faces between the most masculine face (on the right) and the most feminine face (on the left) represent variations in levels of hormones, like testosterone and estrogen, that are associated with attractive male and/or female facial features. (courtesy of Dr. Victor Johnston)

Human pheromones - Androstenone (5alpha-androst-16-en-3-one) :-



Androstenone is common in humans and in pigs, which is the source of some of the erroneous "pig pheromone" claims. This pheromone is found in both men and women, is predominantly known of as a male pheromone. This is because it typically creates a dominant, intimidating, aggressive aura. Therefore, pheromone products containing this are likely to project an aggressive alpha impression (either alpha male or female), which might help you to be the centre of attention and be noticed more. Since alpha aggressiveness is often associated with sex and good mate choice, this pheromone can create a sexual vibe and increase sexual tension. To cause members of the opposite sex to become slightly intimidated by you can be attractive, so this pheromone helps in this regard too. Androstenone has also been known to cause people to act more respectfully and polite to the wearer.

Be sure to wear an adequate cover fragrance over or near any androstenone applications, this pheromone has quite a pungent stale sweat/urine smell in high concentrations.

An over dose (OD) of andostenone can cause:


Bad smelling applications

Aggression from other members of the same sex

An aggressive mood in the wearer

Members of the opposite sex to be overly intimidated, leading to no or even negative reactions.

Alpha-Androstenol (5alpha-androst-16-en-3-ol):-


The alpha isomer of Androstenol creates a friendly approachably impression, and can make the wearer seem less intimidating and more approachable. It seems to be more of a neurotic chatty pheromone than the beta isomer, touching more on empathy and romantic feelings. Androstenol also creates an aura of youth and health, which can help to create an impression of reproductive fitness, which is attractive.

The primary reported response to Androstenol or Androstenol containing products has been an increase in chattiness and friendliness from both sexes, but as mentioned above it can increase sexual attractiveness as well. It has been referred to as an "ice-breaker" pheromone.

An over dose (OD) of Androstenol can cause:


A feeling akin to a kind of drunken tiredness

An impression of weakness. In other words, making you appear a lot less alpha

Human pheromones - Androsterone


Androsterone is a human only pheromone. It's use as a pheromone is born out of the fact that males with a higher ratio of Androsterone to Etiocholanone are more masculine. Homosexual males have lower ratios of Androsterone to Etiocholanone. Thus, androsterone makes the wearer appear to be more masculine and/or dominant, but without the aggression of androstenone. This pheromone also creates an aura of safety, protection and reliability normally associated with a more peaceful alpha male. Androsterone also provides the respect of androstenone without the possible negative connotations of the aggressive nature of androstenone.

When worn by women, androsterone has been reported to have mood elevating effects.

Through experimentation, some users have reported that androsterone can enhance or boost the message that other pheromones in a product or pheromone mix are signaling.

There are no known over dose effects for androsterone.

Human pheromones - Androstadienone (delta 4,16-androstadien-3-one)


This is a pheromone that is widely documented to have a very specific effect on the brain activity of women. One particular study has shown that it affects attention and social cognition areas of the brain. It is also one of the only pheromones that has been shown to stimulate the VNO, and so has been described as a vomeropherin.

Androstadienone, more commonly known as A1, is a very popular pheromone within the pheromone community. One of it's more remarkable effects is that it can elevate a woman's mood, and even alleviate PMS stress! It has been known to increase intimacy and comfort, and can also increase caring feelings. It has been called the "love pheromone" because of the nature of the feelings and reactions it induces in women, and also because of it's usefulness in more cozy relationship situations.

There are no known over dose effects for Androstadienone (A1), but it does convert to androstenone over time on the skin so an OD risk can be created this way.

Human pheromones - Copulins


Copulins are an exclusively female group of pheromones. There are secreted into the vagina at the optimum ratios during ovulation with the aim of encouraging men to desire to copulate. This group of pheromones primarily consists of fatty acids that would serve little to no function on there own, but in combination they have been shown to increase testosterone levels in men by 150% (Astrid Jutte study). This increase in testosterone may cause feelings of arousal in men if a woman is present. It is said that once a man smells Copulins on a woman she is deemed to be more attractive.

Typical reactions from Copulins will be consistent with male indications of interest.

 Human pheromones - Estratetraenol (estra-1,3,5(10),16-tetraen-3-ol):-


This is supposedly the female equivalent to androstadienone (A1), but it's availability is even less than that of androstadienone (A1). Like A1, it stimulates the VNO. It may also have some mood elevating properties in men.

nd Face Preference


During the past 40 years, pheromones of hundreds of insect species have been chemically elucidated, including the sex pheromone of the codling moth. Its main component is (E,E)-8,10-dodecadien-1-ol, a primary alcohol containing a straight chain of 12 carbons and two conjugated double bonds. Other moth pheromones are hydrocarbons, epoxides, acetates or aldehydes. These molecules all vaguely resemble fatty acids, from which they are indeed biogenetically derived.

Most pheromones consist of blends of two or more chemicals which need to be emitted at exactly the right proportions to be biologically active. The female effluvia or sex gland can contain additional compounds which are related to the pheromone components and whose Pheromones are volatile chemical compounds secreted by insects and animals. They act as chemical signals between individuals influencing physiology and behavior in a manner similar to hormones. Pheromones are important to a variety of behaviors including mate attraction, territorality, trail marking, danger alarms, and social recognition and regulation.

The term pheromone is derived from the Greek words pheran (to transfer) and horman (to excite). In animals, they are produced in special glands and are released through body fluids, including saliva and perspiration. Most pheromones are biogenetically derived blends of two or more chemicals that must be emitted in exact proportions to be biologically active.

There is a remarkable diversity in the stereochemistry of pheromones. Insects are sensitive to and utilize chirality to sharpen the perception of pheromone messages. The configurations of pheromones are critical. Stereoisomers of pheromones, for example, can also be inhibitors of the pheromone action.

Pheromones are found throughout the insect world. They are active in minute amounts. In fact, the pheromones released by some female insects (e.g., Silkworm Moth) are recognized by the male of the species as far as a mile away. The pheromone secreted by the female gypsy moth can be detected by the male in concentrations as low as one molecule of pheromone in 1x1017 molecules of air. Insects detect pheromones with specialized chemosensory organs.

At close range, pheromones continue to be released dictating specific behaviors. Another common example of pheromones in action is the trailing behavior of ants. Scout ants release pheromones that guide other ants to the location of food. In boars, pheromones found in boar saliva are known to cause the female to assume a mating position.

An increasingly important use of pheromones involves the control of insects. Because insects rely on phermomones, these compounds have been used by farmers as a method to control harmful insects. Using insect sex attractant pheromones, scientists have been able to produce highly specific traps and insecticides.

Pheromone traps are used to control the insects such as the European corn borer that damages millions of dollars of crops each year. The European corn borer larvae feed on and bore into the corn plant. Cavities produced by borers reduce the strength of the corn and interfere with plant physiology, including the translocation of water and nutrients. European corn borer pheromone traps contain a substance that mimics (i.e., acts like) a part of the chemical communication system used by female moths when they are are receptive to mating. Male moths are attracted to and captured by the pheromone trap that is coated with a sticky substance that retains attracted insects.

Research continues on insect pheromones. It is believed that these compounds hold the key to developing insecticides that can kill only harmful insects while being harmless to humans and beneficial insects.

The search for human aphrodisiacs (stimulants to sexual response) is as old as human history. Although the scientific evidence with regard to human pheromones is contradictory and highly debatable, pheromones are often used as an olfactory aphrodisiac in fragrances and perfumes.

The first discovery related to human pheromones was reported the early 1970s. At this time low molecular weight aliphatic acids, called copulins, were found in the vaginal secretion of women. At the time, it was believed that these compounds could stimulate male sexual response. They were thought to work as did their chemical counterparts excreted by monkeys, baboons and chimpanzees. In the late 1970s more alleged human pheromones were discovered in human perspiration and urine. Some studies suggest a role for pheromones in the regulation and synchronization of the human female menstrual cycle.

The organ responsible for detecting pheromones in animals is a chemosensory structure in the nose called the vomeronasal organ (VNO). In lower animals, this organ detects substances that mediate sexual and territorial behaviors in species. It was once generally believed that humans did not have a VNO. Embryological texts asserted that this organ disappeared during embryonic development. In the 1980s, however, investigations refuted this alleged disappearance. Subsequent research suggested that a functioning VNO was present in near two small holes on the hard divider in the nose. A group of cells similar to nerve cells are located behind these holes. These cells, which make up the VNO, transmit a signal to the hypothalamus in the brain. The stimulating effect on the hypothalamus results in the production of proteins that may influence behavior.

Use for pest control:-

When used in combination with traps, sex pheromones can be used to determine what insect pests are present in a crop and what plant protection measures or further investigations might be in order to assure that there will be no excessive damage to the crop. If the synthetic attractant is exceptionally seducing and the population level is very low, some control can be achieved with pheromone traps or with a technique called "attract and kill".

Generally, however, a technique called mating disruption is more effective: Synthetic pheromone is released from numerous sources placed throughout the crop to be protected; the males are then unable to locate the females and the number of matings and offsprings is reduced.


Mating disruption is effective in:

pink bollworm

Pectinophora gossypiella

Oriental fruit moth

Grapholita molesta

European grape moth

Eupoecilia ambiguella

grapevine moth

Lobesia botranaMating disruption has been successful in controlling a number of insect pests. More than 20% of the grape growers in Germany and Switzerland employ this technique and produce their wine without using insecticides. If you are interested in this technique, you could look at the proceedings of conferences held by the Working Group "Use of pheromones and other semiochemicals in integrated control" of the International Organization of Biological Control (IOBC).

In this database we have included, species by species, any reports on sex pheromones and related chemicals that were thought to be of value to scientists interested in identifying Lepidoptera pheromones, studying biosynthetic pathways or using pheromones for insect monitoring and control. Not included are pheromones produced by males, such as aphrodisiacs and arrestants.

Insects pheromones

With pride and satisfaction, a farmer eyes the glistening red globes of the tomatoes he has just harvested. A few years ago he had been ready to abandon tomato farming because the destructive tomato pinworm was ruining as much as two-thirds of his crop. Despite his zealous use of insecticides, these worms would tunnel into his tomatoes, leaving telltale pinholes and unsightly black blotches that destroyed the crop's marketability.

But now, spiraling around the stems of many of his tomato plants, are dispensers of a potent chemical guardian. These hollow plastic tubes emit a chemical that interferes with the ability of the pinworm moth to find mates, and breaks the cycle of infestation. Thanks to pinworm birth control, the farmer was able to bring three-quarters of his crop to market this year.

The farmer's success story is the result of more than a century's worth of investigation by entomologists and chemists bent on solving such mysteries as how a moth lures mates from far and wide, or how an ant lets her whole colony know the location of a food source. Scientists looking for new methods of pest management then expanded on this basic research. As a result, farmers of many kinds of crops now have highly effective weapons for their perennial battle against insect pests.

The new weapons use chemical substances generated by the insects themselves. Unlike conventional pesticides, the chemicals, known as pheromones, do not damage other animals, nor do they pose health risks to people. Pheromones specifically disrupt the reproductive cycle of harmful insects. They also can be used to lure the pests into traps that help farmers track insect population growth and stages of development. In this way, farmers can reduce the amount of insecticide they need - spraying only when the insects are in a vulnerable stage or when their numbers exceed certain levels.

A Seductive Scent:-

One May morning in the 1870s, the French naturalist Jean-Henri Fabre was pleased when a female great peacock moth emerged from a cocoon on a table in his laboratory-study. He put her under a wire-gauze bell-jar and left her to spread her wings to dry. Around nine o'clock that evening Fabre's pleasure turned to amazement as dozens of male great peacocks, with striking eyespots on wings as much as 6 inches across, floated in through the open doors and windows of the house. "Coming from every direction and apprised I know not how," Fabre wrote, "here are forty lovers eager to pay their respects to the marriageable bride born that morning amid the mysteries of my study." Over the following week Fabre caught more than 150 males. No matter where in the house he moved the female, the male moths made directly for her. What was drawing them, he wondered?

Over the next several years Fabre carried out painstaking experiments to learn the moths' secret. Eventually, he concluded that, even though no human nose could detect it, the female moth must release an odor that is powerfully attractive to the opposite sex of her species.

New York entomologist Joseph A. Lintner came to the same conclusion a short time later when he created a spectacle by placing a female spicebush silk moth on his office window sill. Within minutes a crowd of large brown male spicebush silk moths, with wingspans of up to 4 inches, began making their way toward the window sill. Fifty male moths were drawn to the female, in turn attracting a large crowd of amazed people on the sidewalk below.

Finding Hidden Chemicals:-

Given the techniques available to chemists at the end of the nineteenth century and the beginning of the twentieth, the mysterious substances remained elusive. Then, in the 1930s, a persistent German chemist at the Kaiser Wilhelm Institute for Biochemistry in Germany decided to tackle the problem.

Adolph Butenandt had already made a name for himself by discovering the human sex hormones estrone, testosterone, and progesterone. Branching out into a different arena, he aimed to discover the substance that female moths use to attract males. Butenandt thought the work would open up an entirely new field of research, and like Lintner, he envisioned this research creating a new way to control insect pests.

Butenandt pursued his goal throughout the years of Hitler's regime, World War II, and Germany's long recovery after the war. The task was difficult. He began by snipping off the abdominal tips of virgin female silkworm moths and grinding them up. Then, using analytical chemistry techniques, he separated the moth slurry into various extracts and tested each one on male silkworm moths. The domesticated silkworm moth has lost its ability to fly. But the male will flutter his wings when excited by a nearby female-and when fooled by one of Butenandt's extracts.

Working over the course of nearly three decades, Butenandt ground up about half a million female silkworm moths in his quest to identify their alluring perfume. At last in 1959, he announced success: The substance was a kind of alcohol that Butenandt christened bombykol, after the moth's Latin name, Bombyx mori.

That same year German biochemist Peter Karlson and Swiss entomologist Martin Lüscher introduced the term "pheromone" (Greek for "carrier of excitement"). The researchers were working on identifying the chemicals that maintain the elaborate caste system of termites, and they coined the word to describe a substance that an animal gives off to trigger a specific behavioral or developmental reaction in another member of the same species.

Butenandt's successful characterization of an insect pheromone inspired others to undertake the tedious effort required to seek out the pheromones made by other insects.

Behavioral assays, such as the wing-fluttering response used by Butenandt, remained key to identification of pheromones throughout the 1960s. For example, in 1961, Colin G. Butler at the Rothamsted Experimental Station in London used a behavioral assay to identify a pheromone that regulates the physiological development of an insect, specifically the honey bee. Scientists knew that queen bees emit a substance that stops worker bees from rearing other queens. Butler tested mandibular gland secretions to determine whether they inhibited worker bees from constructing specialized queen rearing chambers. Through this behavioral assay he identified a pheromone produced by the queen bee that would not only suppress the rearing of queens, but also halt the development of the worker bees' ovaries.

Scientists quickly turned their attention from studying beneficial insects, such as the silk moth and the honey bee, to investigating pestiferous insects. Using behavioral assays, researchers identified the pheromones used as attractants by the black carpet beetle, the California 5-spined engraver beetle, the western pine beetle, the cabbage looper moth, and a leaf-cutting ant, among others.

Many scientists were frustrated in their search for pheromones. Further progress would depend on the development of new methods and approaches. Was there, for example, another more general test for pheromones?

Researchers had been pondering the question for some time. As early as 1953, Peter Karlson had suggested to his neighbor, biologist Dietrich Schneider, that he use his expertise in electrophysiology to develop an electrical means of detecting pheromones.

Schneider took up the challenge. At the time biologists suspected that the large furry antennae of many moth species enabled them to detect pheromone molecules in the air. Schneider came up with the brilliant idea that he could use the antennae as "sniffers" for pheromones, reasoning that they might respond to a relevant chemical with a small burst of electrical activity, a characteristic response of nerve cells when stimulated.

Schneider removed an antenna from a male silk moth, bathed it in a saline solution to keep its cells fresh, and lodged it between two electrodes, devices that sense electrical activity. He then gave the antenna a whiff of air that swept past an extract containing bombykol (graciously provided by Butenandt's lab). The biologist was thrilled to note a peak of electrical activity in the antenna corresponding to exposure to the extract. Schneider named this odor-prompted electrical response of an insect antenna an "electroantennogram" (EAG). He reported his technique in 1957.

A Vanishing Act:-

Despite these successes, pheromone research still proved frustrating for many. Extracts that were highly attractive to male insects when left in their crude form mysteriously lost their allure when purified into their various components. And in many cases, synthetic compounds that passed the pheromone test in the lab failed abysmally to attract male moths in the field.

Clues to why this was so began surfacing in the mid 1960s in the laboratory of chemist Robert Silverstein, then at Stanford Research Institute in California. Silverstein was collaborating with entomologist David Wood at the University of California, Berkeley, to identify the pheromone that spurs both male and female bark beetles (specifically, Ips confusus) to colonize specific pine trees en masse. As the beetles tunnel through the bark of trees this "aggregation" pheromone draws ever larger crowds of beetles to overwhelm the tree's defenses, such as the resin that oozes from wounds.

Wood determined that the pheromone lurked in the sawdust-like mixture of wood borings and fecal pellets the beetle expels out of its excavation tunnel. He sent almost ten pounds of this potent mixture, known as "frass," to Silverstein, who set out to analyze its components.

Silverstein and Wood assessed which portion of the frass contained the pheromone by seeing which extract spurred beetles to walk upwind toward it. When they broke down that attractive portion into its three main chemical compounds, they found that each individually had no effect on the beetles; however, when they combined two of the components, the attractiveness to beetles was restored in laboratory tests.

Encouraged, Silverstein and Wood tested the two-component mixtures out in the field. In a surprising development, their tests failed to attract the intended bark beetle but instead attracted another species, Ips latidens. But when they re-combined all three components and used that mixture as a lure, they trapped as many of the intended bark beetles as they did when using live beetles as bait. This mixture was no longer attractive to Ips latidens, demonstrating an interruption of attraction response by the addition of the third component.

The findings were a revelation to pheromone researchers. Although the notion of testing every fraction of a mixture in combination with every other fraction made pheromone research more complex, it also helped to explain many failures of the past. During the 1970s, several scientists reanalyzed the pheromones that had fared well in the laboratory yet failed in the field. Often they discovered that the addition of one or two more components to these single compounds improved field test results tremendously.

Amazingly the missing component sometimes had the same assortment of atoms joined to give the same chemical structure, but the shape was its mirror image. In other cases the mirror image of the pheromone had an opposite effect. In Japanese beetles, for example, contamination of its sex pheromone with just 1 percent of its mirror image compound dramatically diminishes its attractiveness. Researchers also discovered that for many insects, if the pheromone components are not combined in the proper proportions, the mixture loses its attractiveness-or attracts a different species

'Scientific Discoveries' On Pheromones

Miller and Maner (2009) helps to establish the link from human pheromones to behavior. It shows that human pheromones elicit changes in hormone levels. There's a well detailed pathway to changes in testosterone (T) that starts with gene activation in hormone-secreting cells of hypothalamic tissue in the brain, which is the organ that controls our behavior. What this means is that human pheromones are chemicals found in our social environment that directly activate a gene-cell-tissue-organ-organ system pathway, which directly links pheromones to behavior.

Scent of a Woman (from Psychological Science)

by Saul L. Miller and Jon K. Maner

female moths which are used to attract conspecific males for mating. Bombykol, the sex pheromone of the silkmoth, was first synthesized in 1959.

The drawing on the left, by Peter Fluri, shows a female of the codling moth, Cydia pomonella, raising her abdomen and protruding her sex gland. She takes this calling posture for a short period in the early evening hours. Codling moth males casting through the apple orchards will eventually be caught in the plume of a calling female, get aroused and steer upwind until they find her and mate with her. 








2:-Ebook of pheromones