pheromone pheromone a pheromone (from ancient greek φέρω (phérō) 'to bear', and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. there are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. their use among insects has been particularly well documented. in addition, some vertebrates, plants and ciliates communicate by using pheromones. the ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology. a fanning honeybee exposes nasonov's gland (white – at tip of abdomen) releasing pheromone to entice swarm into an empty hive background the portmanteau word "pheromone" was coined by peter karlson and martin lüscher in 1959, based on the greek φερω pheroo ('i carry') and ὁρμων hormon ('stimulating'). pheromones are also sometimes classified as ecto-hormones. they were researched earlier by various scientists, including jean-henri fabre, joseph a. lintner, adolf butenandt, and ethologist karl von frisch who called them various names, like for instance "alarm substances". these chemical messengers are transported outside of the body and affect neurocircuits, including the autonomous nervous system with hormone or cytokine mediated physiological changes, inflammatory signaling, immune system changes and/or behavioral change in the recipient. they proposed the term to describe chemical signals from conspecifics that elicit innate behaviors soon after the german biochemist adolf butenandt had characterized the first such chemical, bombykol, a chemically well-characterized pheromone released by the female silkworm to attract mates. categorization by function aggregation aggregation of bug nymphs aggregation of the water springtail podura aquatica aggregation pheromones function in mate choice, overcoming host resistance by mass attack, and defense against predators. a group of individuals at one location is referred to as an aggregation, whether consisting of one sex or both sexes. male-produced sex attractants have been called aggregation pheromones, because they usually result in the arrival of both sexes at a calling site and increase the density of conspecifics surrounding the pheromone source. most sex pheromones are produced by the females; only a small percentage of sex attractants are produced by males. aggregation pheromones have been found in members of the coleoptera, collembola, diptera, hemiptera, dictyoptera, and orthoptera. in recent decades, aggregation pheromones have proven useful in the management of many pests, such as the boll weevil (anthonomus grandis), the pea and bean weevil (sitona lineatus, and stored product weevils (e.g. sitophilus zeamais, sitophilus granarius, and sitophilus oryzae). aggregation pheromones are among the most ecologically selective pest suppression methods. they are non-toxic and effective at very low concentrations. alarm some species release a volatile substance when attacked by a predator that can trigger flight (in aphids) or aggression (in ants, bees, termites) in members of the same species. for example, vespula squamosa use alarm pheromones to alert others to a threat. in polistes exclamans, alarm pheromones are also used as an alert to incoming predators. pheromones also exist in plants: certain plants emit alarm pheromones when grazed upon, resulting in tannin production in neighboring plants. these tannins make the plants less appetizing to herbivores. epideictic epideictic pheromones are different from territory pheromones, when it comes to insects. fabre observed and noted how "females who lay their eggs in these fruits deposit these mysterious substances in the vicinity of their clutch to signal to other females of the same species they should clutch elsewhere." it may be helpful to note that the word epideictic, having to do with display or show (from the greek 'deixis'), has a different but related meaning in rhetoric, the human art of persuasion by means of words. territorial laid down in the environment, territorial pheromones mark the boundaries and identity of an organism's territory. in cats and dogs, these hormones are present in the urine, which they deposit on landmarks serving to mark the perimeter of the claimed territory. in social seabirds, the preen gland is used to mark nests, nuptial gifts, and territory boundaries with behavior formerly described as 'displacement activity'. trail social insects commonly use trail pheromones. for example, ants mark their paths with pheromones consisting of volatile hydrocarbons. certain ants lay down an initial trail of pheromones as they return to the nest with food. this trail attracts other ants and serves as a guide. as long as the food source remains available, visiting ants will continuously renew the pheromone trail. the pheromone requires continuous renewal because it evaporates quickly. when the food supply begins to dwindle, the trail-making ceases. pharaoh ants (monomorium pharaonis) mark trails that no longer lead to food with a repellent pheromone, which causes avoidance behaviour in ants. repellent trail markers may help ants to undertake more efficient collective exploration. the army ant eciton burchellii provides an example of using pheromones to mark and maintain foraging paths. when species of wasps such as polybia sericea found new nests, they use pheromones to lead the rest of the colony to the new nesting site. gregarious caterpillars, such as the forest tent caterpillar, lay down pheromone trails that are used to achieve group movement. sex male danaus chrysippus showing the pheromone pouch and brush-like organ in kerala, india in animals, sex pheromones indicate the availability of the female for breeding. male animals may also emit pheromones that convey information about their species and genotype. at the microscopic level, a number of bacterial species (e.g. bacillus subtilis, streptococcus pneumoniae, bacillus cereus) release specific chemicals into the surrounding media to induce the "competent" state in neighboring bacteria. competence is a physiological state that allows bacterial cells to take up dna from other cells and incorporate this dna into their own genome, a sexual process called transformation. among eukaryotic microorganisms, pheromones promote sexual interaction in numerous species. these species include the yeast saccharomyces cerevisiae, the filamentous fungi neurospora crassa and mucor mucedo, the water mold achlya ambisexualis, the aquatic fungus allomyces macrogynus, the slime mold dictyostelium discoideum, the ciliate protozoan blepharisma japonicum and the multicellular green algae volvox carteri. in addition, male copepods can follow a three-dimensional pheromone trail left by a swimming female, and male gametes of many animals use a pheromone to help find a female gamete for fertilization. many well-studied insect species, such as the ant leptothorax acervorum, the moths helicoverpa zea and agrotis ipsilon, the bee xylocopa sonorina, the frog pseudophryne bibronii, and the butterfly edith's checkerspot release sex pheromones to attract a mate, and some lepidopterans (moths and butterflies) can detect a potential mate from as far away as 10 km (6.2 mi). some insects, such as ghost moths, use pheromones during lek mating. traps containing pheromones are used by farmers to detect and monitor insect populations in orchards. in addition, colias eurytheme butterflies release pheromones, an olfactory cue important for mate selection. the effect of hz-2v virus infection on the reproductive physiology and behavior of female helicoverpa zea moths is that in the absence of males they exhibited calling behavior and called as often but for shorter periods on average than control females. even after these contacts virus-infected females made many frequent contacts with males and continued to call; they were found to produce five to seven times more pheromone and attracted twice as many males as did control females in flight tunnel experiments. pheromones are also utilized by bee and wasp species. some pheromones can be used to suppress the sexual behavior of other individuals allowing for a reproductive monopoly – the wasp r. marginata uses this. with regard to the bombus hyperboreus species, males, otherwise known as drones, patrol circuits of scent marks (pheromones) to find queens. in particular, pheromones for the bombus hyperboreus, include octadecenol, 2,3-dihydro-6-transfarnesol, citronellol, and geranylcitronellol. sea urchins release pheromones into the surrounding water, sending a chemical message that triggers other urchins in the colony to eject their sex cells simultaneously. in plants, some homosporous ferns release a chemical called antheridiogen, which affects sex expression. this is very similar to pheromones. other this classification, based on the effects on behavior, remains artificial. pheromones fill many additional functions. nasonov pheromones (worker bees) royal pheromones (bees) calming (appeasement) pheromones (mammals) necromones, given off by a deceased and decomposing organism; consisting of oleic and linoleic acids, they allow crustaceans and hexapods to identify the presence of dead conspecifics. suckling: taa is present in rabbit milk and seems to play a role of pheromone inducing suckling in the newborn rabbit. categorization by type releaser releaser pheromones are pheromones that cause an alteration in the behavior of the recipient. for example, some organisms use powerful attractant molecules to attract mates from a distance of two miles or more. in general, this type of pheromone elicits a rapid response, but is quickly degraded. in contrast, a primer pheromone has a slower onset and a longer duration. for example, rabbit (mothers) release mammary pheromones that trigger immediate nursing behavior by their babies. primer primer pheromones trigger a change of developmental events (in which they differ from all the other pheromones, which trigger a change in behavior). they were first described in schistocerca gregaria by maud norris in 1954. signal signal pheromones cause short-term changes, such as the neurotransmitter release that activates a response. for instance, gnrh molecule functions as a neurotransmitter in rats to elicit lordosis behavior. pheromone receptors in the olfactory epithelium further information: trace amine-associated receptor the human trace amine-associated receptors are a group of six g protein-coupled receptors (i.e., taar1, taar2, taar5, taar6, taar8, and taar9) that – with exception for taar1 – are expressed in the human olfactory epithelium. in humans and other animals, taars in the olfactory epithelium function as olfactory receptors that detect volatile amine odorants, including certain pheromones; these taars putatively function as a class of pheromone receptors involved in the olfactive detection of social cues. a review of studies involving non-human animals indicated that taars in the olfactory epithelium can mediate attractive or aversive behavioral responses to a receptor agonist. this review also noted that the behavioral response evoked by a taar can vary across species (e.g., taar5 mediates attraction to trimethylamine in mice and aversion to trimethylamine in rats). in humans, htaar5 presumably mediates aversion to trimethylamine, which is known to act as an htaar5 agonist and to possess a foul, fishy odor that is aversive to humans; however, htaar5 is not the only olfactory receptor that is responsible for trimethylamine olfaction in humans. as of december 2015, htaar5-mediated trimethylamine aversion has not been examined in published research. in the vomeronasal organ in reptiles, amphibia and non-primate mammals pheromones are detected by regular olfactory membranes, and also by the vomeronasal organ (vno), or jacobson's organ, which lies at the base of the nasal septum between the nose and mouth and is the first stage of the accessory olfactory system. while the vno is present in most amphibia, reptiles, and non-primate mammals, it is absent in birds, adult catarrhine monkeys (downward facing nostrils, as opposed to sideways), and apes. an active role for the human vno in the detection of pheromones is disputed; while it is clearly present in the fetus it appears to be atrophied, shrunk or completely absent in adults. three distinct families of vomeronasal receptors, putatively pheromone sensing, have been identified in the vomeronasal organ named v1rs, v2rs, and v3rs. all are g protein-coupled receptors but are only distantly related to the receptors of the main olfactory system, highlighting their different role. evolution olfactory processing of chemical signals like pheromones exists in all animal phyla and is thus the oldest of the senses. it has been suggested that it serves survival by generating appropriate behavioral responses to the signals of threat, sex and dominance status among members of the same species. furthermore, it has been suggested that in the evolution of unicellular prokaryotes to multicellular eukaryotes, primordial pheromone signaling between individuals may have evolved to paracrine and endocrine signaling within individual organisms. some authors assume that approach-avoidance reactions in animals, elicited by chemical cues, form the phylogenetic basis for the experience of emotions in humans. avoidance of inbreeding mice can distinguish close relatives from more distantly related individuals on the basis