We found him with five partners, each of a different world and sex
The Shore Police were on the way — we had no second chance.
We beamed him up in the nick of time — in the remnants of his pants!
An alien species' sex system is very bizarre in comparison with terrestrial ones. Perhaps it has two sexes that are not identifiable as either "male" or "female" in terrestrial terms, or perhaps it has three or more sexes, each of whom is indispensable for the species' reproduction process.
Of course, Earth has a few bizarre examples of its own. Some species of fungi have more than two sexes (although only two at a time are required for reproduction). There's a species of fish that only has one sex, and among seahorses, the male bears the children. But this only scratches the surface of what writers can imagine.
Supertrope of One-Gender Race. Subtrope of Bizarre Alien Reproduction. May lead to Pronoun Trouble. Compare Bizarre Sexual Dimorphism, Exotic Equipment, Non-Human Non-Binary, and Extra Parent Conception. Contrast No Biological Sex. May be used as part of a Speculative Fiction LGBT story.
- In Phil Foglio's Buck Godot: Zap Gun for Hire's "The Gallimaufry" storyline, a male alien Pog member named Qvakk states that he loved Oort, another male member of his race/species, and was "gonna take him home, make lots of eggs".
- In ODY-C, the backstory includes a Gendercide that wiped out all male humans, and an attempt to fill the gap that resulted in the creation of a new gender, "sebex", who look like Pink Skinned Space Babes and get pregnant by sex with women.
- Alpha/Beta/Omega (also known as Omegaverse) is an odd genre of erotica built around a mixture of this trope and Fantastic Caste System, usually applied either to werewolves (which is where the trope originated, specifically in the Supernatural fandom) or to the setting's version of humans. In keeping with the Alpha and Beta Wolves trope, alphas are sexually dominant, omegas are sexually submissive, and betas (when they appear) are generally in the middle of the hierarchy. Omegas bear children from alphas (and sometimes from betas) and often pair bond with alphas too. To make matters more confusing, this trope gets combined with real human sexes, so omega males can get pregnant and alpha females can sometimes impregnate omegas. (Meanwhile, betas tend to have anatomy more typical of real humans.) You'll also commonly see canine sexual traits, like heat in omegas and knotting in alpha males. Many an Alternate Universe Fic inserts existing characters into such a setting and assigns them roles in the caste system. Lindsay Ellis goes into detail about it here.
- In Dæmorphing, Taxxons used to have four sexes, similar to the castes of hive insects: nurses, queens, workers, and soldiers. However, nurses and soldiers are extinct by the time the story begins.
- The silicon-based Jan in Alien in a Small Town have three sexes: the male Workers, who make up the majority of the population; the female Matriarchs, who grow into essentially sessile living mountains and are the leaders of their society, and whose bodies typically contain tunneled passages which are inhabited by other Jan; and the sterile Warriors, who have six arms ending in vicious hooks, huge fanged mouths, and are much much faster and stronger than their Worker counterparts.
- The stsho of the Chanur Novels have three sexes which form mating trios. None of the sexes is quite male or quite female, since a stsho who fulfils the young-bearing role in one mating trio can fulfill a non-young-bearing role in a different trio. Further, if a stsho is subjected to enough psychological stress it might undergo phasing, changing both sex and personality. In addition to the three reproductive sexes, the stsho have five genders: one for each reproductive sex, a fourth for stsho who are undergoing phasing, and a fifth for stsho who are too old to reproduce.
- All Tomorrows has the Temptors. Females are gigantic, immobile, and resemble... er... a penis with immense eyes and beaks. Males are small, vaguely birdlike humanoids who care for the female.
- Bruce Coville:
Gibbons: I am neither male nor female. I'm a farfel.
- Tar Gibbons from the Rod Allbright Alien Adventures series insists on gender neutral pronouns because referring to it as male or female is offensive to it. No details are given.
Rod: Is that more like a boy or more like a girl?
Gibbons: Actually, it's more like a pippik than anything.
- The My Teacher Is an Alien series by the same author has Hoo-Lan, whose species needs five different genders just to get an egg, and three more to hatch it.
- Isaac Asimov:
- The Gods Themselves: The Soft Ones are gaseous aliens with three sexes, "rational", "emotional", and "paternal". Being gaseous, they have sex by literally combining their bodies thus merging the three Soft Ones into a single member of what they thought was a different species, the Hard Ones.
- "Green Patches": The Saybrook organism doesn't understand sexual dimorphism because they can always reproduce asexually, and impregnate anyone capable of gestation and cellular reproduction with their Telepathy. As far as the Saybrook lifeform is concerned, the ship's lifeforms can be divided into sterile ones and life producers.
- In the short story Hop-Friend by Terry Carr, Martians (or "Marshies") are mentioned to have three sexes.
- InCryptid: Laidly worms have four sexes/genders: the humanoid males and females, and the dragonlike drakes and jennys. Unfortunately, only one is left, a female.
- In Isekaid Shoggoth, the main character is a shoggoth and self-identifies as female, because she was raised and disguises herself as a human woman, but the truth is far more complicated. For brevity, she boasts that she's very, very familiar with tentacle play, and it's off-screen.
- Known Space:
- Jotoki are amphibious and look sort of like starfish. They have an immature aquatic stage, and five sexes. Each limb starts as a separate non-sapient creature, which meet and join at maturity, then develop intelligence just before they breed.
- The Puppeteers from the same series claim to have three sexes for PR reasons. The ugly truth is that the "mother" is actually a different species that is parasitized by the Puppeteers in a manner not unlike the larvae of a tarantula hawk.
- Kzin reproduction is close to standard in that they have what we'd recognize as males and females, but the females are non-sentient and basically animals. Male kzinti were enormously confused at meeting other species, such as humans, where both sexes are sapient. It's actually implied that this was not always the case — kzin legends refer to their females having been sapient, once, but they tried to rebel against the Fanged God and lost their souls as punishment. The reality is that after the pre-industrial kzinti destroyed and took the technology of an alien race that landed on their planet, the male kzinti genetically engineered their females to be the way they are now, while at the same time making themselves as strong and vicious as possible to fit with their bronze age ideals of gender roles. A few kzinti populations around Known Space that have been isolated from the homeworld for very long times still have sapient females.
- In Last and First Men, the Eighteenth Men, our many-millions-of-years descendants, have evolved and/or engineered themselves to have as many as ninety-six different sub-sexes.
- Ursula K. Le Guin's The Left Hand of Darkness takes place on a planet (called "Winter") where people have no permanent sex. They are sexless and asexual most of the time, but from puberty on they turn into a male or a female once a month to reproduce. The same person can be male or female on different occasions, so basically everybody on the planet is both a male and a female and neither.
- There is a story by Stanisław Lem about aliens who, among other things, have five sexes.
- In The Long Way to a Small Angry Planet, the aeluon have four sexes: male, female, shon (who switch between male and female) and those who are neither.
- In The Culture novel The Player of Games, the Azadians have three sexes - male, female and apex, a hermaphroditic gender.
- Biologically, all three are required for reproduction: the males impregnate the ovum-producing apexes, who in turn implant the fertilized egg in the females for gestation.
- As one might guess from the name, the apexes are culturally dominant and brutally oppressive of the other genders. Males have the lowest social standing and rights, treated as nothing but Dumb Muscle and military mooks. Females hold more status, but are still second-class-citizens with few rights and privileges (and are in fact widely, but incorrectly, believed by the Azadians not to actually contribute DNA to their offspring).
- In Shadow Man by Melissa Scott, humans in the future have seen a dramatic rise in intersex conditions (due to drugs necessary for space travel) leading to five recognized sexes: male, mem, herm, fem, female (clearly influenced by an article by Anne Fausto-Sterling ) and nine sexual orientations.
- The Tralfamadorians from Slaughterhouse-Five have five sexes - and humans have seven. Most of ours exist only in the fourth dimension.
- In a bizarre case overlapping with No Biological Sex, there are apparently seven genders in The Space Trilogy by C. S. Lewis, two of which correspond both to the human sexes and to the genders of the Oyarsu watching over Mercury, Venus, and Mars. The rulers of those three planets have genders, but also have No Biological Sex... it's complicated. When the Oyarsu of Jupiter and Saturn show up, their genders are neither masculine or feminine, which contributes to their already-formidable case of You Cannot Grasp the True Form.
- Star Trek Expanded Universe:
- In the TOS-era novels by Diane Duane, there is one race, the Sulamid that is described as a bundle of bright purple tentacles about six to seven feet high, topped off with a sheaf of pink-stalked and tentacled eyes with triangular pupils and a purplish, "bloodshot" look. According to Dr. McCoy, they have twelve sexes, and all of them claim to be "male," especially the ones that bear the children. The Enterprise has at least three of them among the crew, Mr. Athende in Maintenance, Lt. Meshav from Data Management, and ensign Hwa'vire from Engineering.
- Diane Duane and AC Crispin also have a recurring Horta officer aboard the Enterprise, Dahai Iohor Naraht, who first appeared in Duane's Rihannsu novels and is described as an "orthomale type B-4A". The Horta are a silicon-based species resembling a mobile rock pile, so it's somewhat understandable that their reproductive methods would look nothing like Earth norms.
- The squales in the Star Trek: Titan novel Over a Torrent Sea have four sexes.
- The Jelna Rigelians in the Star Trek: Enterprise Relaunch novel Tower of Babel have four sexes too—endomale, endofemale, exomale, exofemale. Contrast with Zami Rigelians, who have the usual two sexes, and Rigelian Chelons, who are hermaphrodites but accept gender identities due to centuries of cultural imposition by the Jelna and Zami.
- The Star Trek: The Next Generation episode "Data's Day" has a line that Andorian marriage involves four individuals, leaving it ambiguous as to whether it's this trope or an Exotic Extended Marriage. The Star Trek Novel Verse went with the idea of Andorians having four distinct biological sexes, consisting of chaan and thaan (appear male) and shen and zhen (appear female). In an Andorian bondgroup (shelthreth), the chaan and thaan fertilize the shen, who then transfers the embryo to the zhen to gestate; the zhen does not contribute any genetic material. In a further twist, sexual contact between three or fewer partners is referred to as tezha and considered taboo. This is used to justify the relative dearth of appearances by Andorians; the species suffered tremendous casualties and their overly complex reproductive biology is making it very difficult for them to repopulate.
- Star Wars Legends:
- The Han Solo Trilogy: Hutts, like slugs (their closest real-world equivalent, which is also used as an insult for them), are all hermaphrodites, with both male and female sex organs. While pregnant and rearing their young they identify as female, but apparently can go back to identifying as male later (as Durga's parent Aruk and Jabba's parent Zorba do).
- Black Fleet Crisis: Yevetha have a fairly rare neuter sex along with male and female.
- The listeners from The Stormlight Archive have four sexes, with almost any given individual belonging to two of them over the course of its life. The listeners have the standard two genders (masculine and feminine), but these are each further subdivided into fertile males and females and infertile malen and femalen. To make matters more confusing, the listeners are limited shapeshifters, able to assume any one of several forms to fill various social roles. One of these is the fertile and sex-obsessed mateform.
- Tales of the Jokka: The Jokka created by M.C.A. Hogarth have three genders, anadi (female), emodo (male), and eperu (neuter). They can also change genders up to twice in their lives, the causes aren't entirely clear.
- In The True Meaning of Smekday by Adam Rex, the Boov aliens who attempt to enslave the human race have 7 sexes that translate in English to: girl, boy, boygirl, girlboy, boyboygirl, and boyboyboyboy.
- "Venus and the Seven Sexes", a 1949 short-story by William Tenn, features a seven sexed species that passes gametes in a chain: sex "D" receives from sex "C" and transmits to sex "E." The sex of the offspring is determined by the sex of the parent which receives/completes the fully fertilized gamete. One sex is tasked with coordinating the family.
- Bob Shaw's Warren Peace duology has the Squelchers, an alien race with no less then six different sexes, each one with its own unique appearance, and with a reproductive cycle where each sex fertilizes the others in turn. The forms look so different that, to the vast majority of the universe, the species only consists of the fourth sex, which resembles an orange-haired, saggynote sasquatch with multiple eyes in a ring around its head (usually covered by its fur), oversized feet that let it wade on water, and two giant red nipple-like gamete sacs positioned one above the other on its torso. The fifth sex, the only other one mentioned, is described as being indistinguishable from a tree, except for the presence of a pair of two dual-pronged ovipositors sprouting from its trunk. Their introduction revolves around a plot in which Squelcher workers are wreaking havoc on the delicate, water-based flowers they need to harvest by constantly having orgasms from what their human superiors presume are super-explicit pornography. It turns out that the problem is the staples in the various magazines provided for recreation; they look just like the ovipositors sported by the fifth sex.
- In "Assassin & Son" by Thomas M. Disch, the Sepharadians have seven sexes.
The blobs were septsexual, a degree of sexual differentiation found only in free-form telepathic races. Joseph did not understand too precisely the entire Sephradian mating process. There were, he knew, two blobs that performed a masculine function and two others that could be called women; the "mother" was hermaphroditic, then there were two neutral sexes who served somehow as catalysts. The "neuters" were not motivated by strictly sexual desires: the function of one was largely vegetative and of the other (which Chilperic represented) digestive.
- Lilith's Brood: The Oankali have a third "ooloi" sex, which uses its Biomanipulation powers to create a blastocyst from the male and female partners but doesn't contribute its own genes. Ooloi experience a Metamorphosis akin to a second puberty where they come into their powers, and are a sort of first among equals in their family units.
- According to the Doctor Who Novelisations version of "Creature From the Pit", Tythonians are "tri-sexual", and mate by merging into one creature with six sexes.
- The swales in "That Leviathan, Whom Thou Hast Made" by Eric James Stone have a third, "neuter" sex which facilitates reproduction but does not contribute its own genetic material to the offspring.
- The Hroshii in The Star Beast by Robert A. Heinlein have six sexes.
- The Spicans in the Cluster series by Piers Anthony have three sexes — Impact, Sibilant and Undulant — each of which can play any of the three reproductive roles of Parent, Sire and Catalyst (though procreation always requires one partner of each sex).
- In Mars Evacuees by Sophia McDougall, the Morrors have five sexes and very complex reproductive methods in which a child might have anywhere between three and five parents.
- The Jovians in Three Worlds to Conquer by Poul Anderson have a second type of male called a "demimale"; a female needs to mate with both types within a few hours of each other to conceive.
- The trilaterally symmetrical crab aliens in Their Majesties' Bucketeers by L. Neil Smith have a third sex called a surmale.
- In Tunnels, female Styx (which serve as infiltrators in the Styx's host society) usually look like beautiful females of their host species but grow giant insect legs and ovipositors during the Phase. Meanwhile, male Styx are split into a warrior caste, a civilian caste, and Armagi. The first two castes resemble their host species and don't change during the Phase, though warriors are hatched as larvae from parasitic eggs implanted in members of the host species during the Phase, while civilians are conceived through the host species's normal method of reproduction. If the Phase isn't producing enough warriors to dominate Earth, instead of pupating into their host species's form, warrior larvae will grow into shapeshifting gelatinous Starfish Aliens called Armagi.
- In the Terran Trade Authority universe, Proximans have two sexes; Females, and "Potentials", who are also female(or more accurately, intersex, but their genital sets are "inactive") by default, but have the ability to effectively become male due to certain conditions or the needs of the population. Furthermore, a Potential tends to have a "preferred" option that they usually shift to when mating opportunities come up, but circumstances can change even that
- Star Trek:
- In Star Trek: Voyager the hostile "Species 8472" is reported to have as many as five distinct sexes, at least according to Voyager's medical hologram but he admits they don't know anything else about their reproduction.
- One episode of Star Trek: Enterprise features a race called the Vissians, who as well as having males and females have a third gender called "cogenitors" who are necessary in reproduction but only account for 3% of the population of Vissians. Cogenitors are third class citizens not even given names or an education. They are circulated between couples to assist in reproduction.
- As mentioned under Literature, the Star Trek: The Next Generation episode "Data's Day" has a line that Andorian marriage involves four individuals. Whether or not this trope applies is left uncertain; it's never explicitly stated if it's a case of this trope or if it's a case of Exotic Extended Marriage being phrased ambiguously to get past the censors. The Novelverse went with its own interpretation, explicitly making it this trope, but the TV series has never taken a definitive stance.
- The Goa'uld in Stargate SG-1 are a two-sex race that doesn't match up with Earth norms. The majority of Goa'uld appear to be biologically male but tend to take on the gender identity of their host, with a very small minority being biologically female "queens" that produce larvae. While queens can reproduce asexually, fertilization by a male passes his genetic memory to the offspring; for this reason, what few queens exist are kept as trophy wives by powerful system lords.
- Myriad Song: Elvers have four sexes: male, female, midwife and neuter. Elvers are all born neuter and change to one of the breeding sexes at twenty based on the gender composition of the surrounding community, individuals isolated from others of their species may be neuter for life. Midwife carries fertilized eggs in a pouch and provides hormones.
- Numenera: The skeane — an alien species vaguely resembling emperor penguins with fluke-like, bony tails and six limbs, four ending in seal-like flippers and the front two in webbed hands — have three sexes: egg givers, who produce a small egg once a year; egg takers, who take it into their bodies and brood it until it's ready to hatch; and feeders, who feed the young by regurgitating a special nutrient fluid. These sexes are physically identical to each other in almost all respects, with the only occupation being the presence or absence of white nodules underneath their tails: givers have two, takers four and feeders none.
- Rocket Age: Europans have five genders in total, male (25%), female (25%), neuter (25%) and two unclassified genders (25% collectively). Because the Europans are incredibly secretive, no-one is exactly certain how their reproduction even works and even the classifications Earthlings have given the known genders could turn out to be wildly wrong.
- The insectoid Shirren have male and female members in addition to a third sex called "hosts"; males and females contribute eggs and sperm for reproduction, while the host carries the eggs until the offspring are born in addition to contributing some of their own genes into the trio's young.
- The monkey-like Maraquoi have seven sexes: three "Fathers", a Mother, two "Hosts" (as with the Shirren, but for two different stages in the baby's growth), and what is essentially a "Supervisor" who somehow facilitates everything and somehow gets their DNA in the mix. Maraquoi tend to lean towards pacifism, given how easy it would be for a war to screw over their reproductive cycle.
- Warhammer 40,000: Tyranids don't have defined genders and, due to the way all of their weapons work, would technically qualify as either female or hermaphrodites (their weapons produce and gestates eggs, then launch the resulting creature at the enemy). Anything larger than a bullet would be created via the Norn Queens aboard the Hive Fleets, to which no one knows how the process is suppose to go. Genestealers are even weirder, as they can impregnate host species with their own genetic material, but the host itself still needs to reproduce naturally to pass on said genes effectively giving the child three parents.
- World Tree (RPG): The insectoid Herethroy have three sexes: females, males and co-lovers. The female and male contribute genetic material to the offspring, while the co-lover carries and lays the egg. There are also the rare "both-females", who are capable of playing either the female or the co-lover role in reproduction, although not at the same time. Herethroy marry in triads, but because of uneven gender ratios some genders (co-lovers and males) are allowed or expected to belong to more than one triad at once.
- The Real-Time Strategy Achron has the Grekim, a race of Time Travelling alien cyborg squid with three sexes (octo, pharo, and sepi) and three "classes" (basic, pod, and ligo). Any two members of different sexes may "progenerate" a member of the third sex of the same class or the next one up (e.g. a pharo and a sepi can produce an octo or an octopod, or an octopod and a pharopod can produce a sepipod or a sepiligo). This is the species' primary method of producing units; although the exact details are unclear, a certain amount of proximity is needed but it does not require physical contact. Ligo cannot "progenerate", but can "split down" into two basic units of the remaining genders (e.g. an octoligo can split down into a pharo and a sepi).
- Cthulhu Saves the World has party member Paws, a cat-like alien, explain that his species technically has every member as a unique gender. However, for sake of convenience, he allows the party to refer to him as "he".
- The X-Universe:
- Boron have a third sex, called "Lar", in addition to males and females. The presence of a lar is not strictly necessary for reproduction, but it is described as being "beneficial". Lar prefer to be referred to with female pronouns and it is noted they make up the majority of the Boron leadership.
- The Paranid have 11 sexes. Extra Parent Conception is implied to be required judging by the species fetish for the number three, and the precise parental combination will affect the development of the larva.
- Subnautica: The PDA mentions that every species on the planet 4546B has a single sex which can both fertilize and carry eggs as most of the creatures still need mates to reproduce, however the PDA also states that some of the species are capable of asexual reproduction in case the population gets to low.
- In Starflight 2, the Ng'Kher'Arla is an alien race where the entire species transforms into one of three specific sexes, each with a distinct personality (Arla being friendly, Kher being paranoid, and Ng being hostile and xenophobic), depending on the time of month. On the last day of the month individuals change into a random sex and a species-wide mating orgy ensues.
- Civilized space in Orion's Arm recognizes six Transhuman genders, approximately defined as male, female, hermaphrodite, female pseudohermaphrodite, male pseudohermaphrodite, and genderless. Things pretty much go out the window when you bring actual aliens into the picture.
- The speculative alien species Triaformica has three sexes, due to being descended from fungal ancestors. Likewise, only two sexes are needed to reproduce at any one time.
- Most aliens in the Humans are Space Orcs blog are referred to with nonbinary pronouns. No word on whether these are biological sexes or gender identities, however.
- Serina has the Polymorph Bird, a species with males coming in four different varieties: the large, aggressive Keepers, the smaller, monogamous Ardors, the deceptive, female-mimicking Tramps and the homosexual Bachelors. It's stated that without the other morphs none of them would be able to reproduce: the Tramps require Keepers to trick, for example, otherwise their entire mating strategy would be rendered useless. Even the male-to-male bonding Bachelors play an important role: they steal and adopt the eggs of other heterosexual pairs, which in turn lay replacements, thus actually increasing the fecundity of a population whenever they're around.
- SCP Foundation: The Ad Astra Per Aspera canon has the Taronyu, an alien species with six sexes; each can reproduce with any of the other five.
- Yivo from the Futurama movie The Beast With A Billion Backs is a planet-sized tentacled entity. According to Fry, the creature prefers to be called "shklee" or "shkler", as opposed to "he" or "her".
- According to his Character Blog, Gravity Falls' Bill Cipher's home dimension has 14 billion different genders. He claims that he has not decided on his own orientation simply because of how much paperwork it would entail.
- Home: Adventures with Tip & Oh: In one episode, Oh explains that Boov have 7 genders: boy, girl, boygirl, girlboy, boyboy, boyboygirl and boyboyboyboy.
- Tetrahymena thermophila, a single-celled protozoan, has seven different sexes (or rather, 'mating types', distinguished by a single chromosome) and can mate with any other sex except its own. That way, it increases the chance of finding a suitable partner, as well as provide a wider pallette to mix and match genes and add genetic variety to its offspring.
- Some species of worms have three sexes: males, females, and hermaphrodites. While hermaphrodites are able to ferilize themselves, this produces genetically-identical offspring, so the worms switch between asexual and sexual reproduction to ensure genetic diversity, as well as found new populations without the need for a mate.
- The nematode Caenorhabditis elegans consists of males and hermaphrodites instead of males and females. In the event that a hermaphrodite cannot find a male to mate with, it can self-fertilize.
- The Neotrogla are a genus of Brazillian cave insects known for having reversed sexual organs, females having penises and males having vaginas.
- The Iberian minnow (Squalius alburnoides) consists of two distinct but linked lineages, one consisting only of diploid males and the other consisting of triploid males and females. The diploid males mate with triploid females to produce only diploid male offspring.
- Fungi have over 36,000 sexes, (technically called mating types - think sex-lite) but only two are needed at any one time to reproduce.
- The white-throated sparrow (Zonotrichia albicollis) is moving towards four sexes. Males and females are either white-striped or tan-striped. White-striped males are big philanderers that don't care for their young, butt into others' territory and have high testosterone. White-striped females are aggressive nymphomaniacs who palm off the child-rearing responsibility onto their mates. They're monogamous, though. They always mate with tan-striped birds and the tan-striped birds are more devoted parents, less aggressive and not as horny. And it looks like the chromosome responsible for these differences is turning into a sex chromosome.
- Similarly, the ruff sandpiper has three different male genders: "ordinary" territorial males, "satellite" males that visit mating leks but do not establish territories, and cryptic males ("faeders") that resemble females and rely on the "sneaky bastard" mating strategy. The stark differences in appearance and behavior between these genders appear to be inherited. (Female ruffs appear more attracted to leks with a variety of males present, which explains why the different genders can coexist over the long term, but we can only speculate as to their motives.)
- Side-blotched lizards also have a similar mating strategy, having harem-building Orange males, monogamous Blue males, and sneaky Yellow males. An interesting consequence of this is that the three types are stuck in a Tactical RockPaperScissors scenario: Oranges beat Blues, being bigger and stronger, Yellows beat Oranges, being able to sneak into their harems to mate, and Blues beat Yellows, guarding their single mate and easily chasing off "sneakers".
- Eusociality, which most famously shows up in certain insects like bees and ants, refers to a complex social structure involving reproductive and non-reproductive castes:
- Honeybees famously have three castes: drones, workers, and an Insect Queen. This is related to the development of eggs and larvae. A fertilised egg will become female, either a queen (if raised exclusively on a diet of royal jelly) or a worker. An unfertilised egg will become a male drone that exists to fertilise the queen's eggs and then to die. Eggs laid by queens can be fertilised, while eggs laid by workers can't.
- Many other insect species follow some variant of the drone/worker/queen Hive Caste System, sometimes (especially among ants) further specialising the workers into sub-castes like soldier ants.
- The Cape honeybee (Apis mellifera capensis) reproduces by parasitically cuckolding the better known "killer bee." The Cape honeybees have a unique caste known as a pseudoqueen, which don't work like workers but don't reproduce as often as dedicated queens, which use mind control pheromones to trick the killer bees into killing their own queen and caring for the Cape honeybees. When the host colony eventually dies, the pseudoqueens fly off to find new host colonies and repeat the process.
- Eusociality has even shown up in mammals, specifically the naked mole-rat and the Damaraland mole-rat. In an inversion of how honeybees create queens by boosting a female larva's fertility, mole-rat queens establish their status by releasing hormones that chemically neuter the non-breeding females (and the non-breeding males, in the case of the Damaraland mole-rat). History buffs, picture a Gender Flip of a monarch and his Royal Harem full of concubines and eunuchs.
- In some anglerfish species, males only exist to fuse to a female's body and degenerate into a pair of testicles. This can occur an indefinite number of times, so a female anglerfish can gain an indefinite number of ballsacks. As illustrated by The Oatmeal.