Spider sex is more complex than the binary paradigm

It looks like it’s time for me to go on a blocking rampage on Twitter, because the TERFs/GCs are flooding my account with stupidity. There’s only so much of that that I can take. The problem is that Graham Linehan noticed me, and the flock of dim & bigoted fanatics who follow him are piling on. One of them noticed that I breed spiders and thinks that is an excellent gotcha.

One thing I find gratifying is that sex-denialists like @pzmyers wibble on about sex being socially constructed and bimodal. But when they actually want something done (in this case breed spiders) – they suddenly know there are exactly 2 sexes and it’s the females that make eggs!

I make movies of spiders mating, as he notices, but somehow he thinks I’m a “sex-denialist” and that somehow this contradicts my position on trans rights. Surprise! I actually know how sex works. I understand that making an embryo requires a fusion of two gametes. I would think all of the trans folk he despises would be more conscious of these distinction than he is.

I also know the logical difference between the fact that many females make eggs, and the idea that all females must make eggs. I also know that even in spiders there’s more to sex than tab A goes into slot B.

I also have information on that. I’m mainly interested in spider sex as a means to an end — I need lots of embryos — but to get there I’ve been making observations of spider behavior. Every morning I move a male spider into a container with a female spider, slide it under a dissecting scope, and watch what happens. Sometimes courtship and mating are swift and dramatic, and I click a button and record the whole process, and that’s what you see. Sometimes they take their time, and I have to watch them dawdle and fumble around for a half hour before anything happens. Sometimes I give up and put the pair in an incubator overnight and hope something happens. Rarely, the female just murders and cannibalizes the male. Of the clutch of spiders that emerged in January, I’ve got 11 females who successfully mated and produced an egg sac; I’ve got 16 that spurned the male I provided and are effectively childless. Those I don’t record, because two wallflower spiders avoiding each other isn’t particularly interesting.

What’s going on? I don’t know. My focus isn’t on the behavior, but on the development of embryos. But who knows — maybe there are gay and lesbian spiders. Maybe some are asexual. Maybe there are timid spiders and bold spiders. Maybe some spiders are unattractive and no one wants to have sex with them. Maybe the Adult Spider Female is focused on her bug-munching career, and doesn’t want to make babies. Maybe some pairs of spiders have cellular incompatibilities that prevent fertilization. Maybe for some spiders the behavior works, but the plumbing is atypical. These are all interesting possibilities, and if a student were to come along and ask to make a quantitative analysis of mating behavior and reproductive success, I think there are a lot of good questions to ask and some useful studies to make, because sex, even in a small arthropod as driven by instinct as a spider, isn’t binary, isn’t a question of did they or didn’t they, and exhibits a range of complex variation that I haven’t tried to plumb.

Other people are looking into that! A paper by Angelekakis, Turutzek, and Tuni (2022) looked into mating rates in Parasteatoda, and as I’d expect, it’s complex. Spiders can be choosy — the majority of females didn’t mate at all (as I’m seeing in Steatoda), and many would mate only once and then be done with the whole messy business (they store sperm, so one successful mating is sufficient for a lifetime of egg production.)

As usual, the TERFs/GCs try to ignore all that and shoehorn everything into a simple binary. It doesn’t work for spiders, and it especially doesn’t work for humans, who have layered on so many variations and subtleties and tangled them all up with non-reproductive cultural behaviors. This @nathankw nitwit tried to argue that sex can’t be bimodal because I can’t provide a single numerical parameter that shows a range of values for sex. The problem isn’t that I can’t, it’s that I can provide so many. Receptivity, courtship initiation, web twanging frequency, successful insemination frequency, dancing intensity, abdomen size, interval since last courtship, metabolism levels…I can think of so many measures that don’t exhibit the kind of fixed values that he wants for males and females. It’s overlapping ranges all over the place! In spiders! But he wants to pretend that human sex is simple, nothing but sperm and ova.

Graham Linehan really didn’t have anything to contribute, other than to claim my biology is a religion, and to add this silly little bon mot:

A biologist who pretends to believe that humans can change sex. What a time to be alive.

But if humans can’t change sex, why is this crowd so opposed to gender affirming care, hormonal treatments, and surgery? If sex is an unstoppable freight train that can’t be diverted, then let them continue with their ineffectual efforts to change sex. Except that they keep seeing the inescapable evidence that sex can and does change.

Angelakakis A, Turetzek N, Tuni C (2022) Female mating rates and their fitness consequences in the common house spider Parasteatoda tepidariorum. Ecology and Evolution, doi.org/10.1002/ece3.9678.


  1. birgerjohansson says

    Biologists can probably find many more examples of complexity.
    The Amazon molly, mostly parthenogenic nevertheless has some genetic transfer with a closely related species.
    The anglerfish, where several males physically attache themselves to the female for the rest of their lives and shrink until they are mostly gonads.
    And some fish I forgot that switches gender as it grows.

  2. Reginald Selkirk says

    I also know that even in spiders there’s more to sex than slot A goes into slot B.

    You should fix that. It’s tab A into slot B.

  3. Akira MacKenzie says

    But if humans can’t change sex, why is this crowd so opposed to gender affirming care, hormonal treatments, and surgery?

    Because they believe that those procedures are only cosmetic and are, at best, a form of deprived surgical mutilation. To them, the only true measure of a human female is the agility to crap out a brat.

  4. rietpluim says

    The GC position in short: spiders mate, therefore bigotry.

    This is even more stupid than the lobster thing from that guy from Canada.

  5. StevoR says

    @1. birgerjohansson : ” some fish I forgot that switches gender as it grows.”

    Quite a few fish species actually including these :


    Then there’s the vegetarian* shark that had a virgin birth :


    The female bonnethead shark (Sphyrna tiburo) is able to give birth without having sex. Parthenogenesis, Greek for ‘virgin birth’, had never been recorded in cartilaginous fish until a bonnethead gave birth in a zoo aquarium in Omaha in 2007. Her tank mates were two other female bonnethead sharks and an assortment of rays, so who (or indeed where) was the daddy?

    Female sharks have the ability to store sperm for months, if not years, so it was assumed this shark must have mated prior to being taken captive. The aquarium soap saga continued when the pup was killed by a stingray after just a few days. The unfortunate tragedy gave researchers the opportunity to do genetic analysis, revealing there was no ‘DNA of male origin’ in the baby shark.

    Although its not the only example of that & one’s have been known to give virgin birth even with males around :


    Scientists are baffled after spotting a female zebra shark in an aquarium having given “virgin birth” to pups – meaning she reproduced without mating with a male. ..(snip)… As of yet, scientists have assumed that vertebrates that usually reproduce sexually turn to parthenogenesis as a “hail Mary pass”, a last-ditch effort at reproduction when there aren’t enough mates to go around.

    But in the case of the female zebra shark, the Shedd Aquarium in Chicago insisted that there were healthy, reproductive males in the same enclosure as she.

    .* Okay, strictly speaking omnivorous not “vegentarian but it seems they really do eat and get nutrition from seagrass :

    Bonnetheads also ingest large amounts of seagrass, which has been found to make up around 62.1% of gut content mass. The species appear to be omnivorous, the only known case of plant feeding in sharks.[6] The shark may perform this activity to protect its stomach against the spiny carapaces of the blue crab which it feeds on.[7] A 2018 study with a carbon isotope-labelled seagrass diet found that they could digest seagrass with at least moderate efficiency, with 50±2% digestibility of seagrass organic matter, and had cellulose-component-degrading enzyme activity in their hindgut.

    Source : https://en.wikipedia.org/wiki/Bonnethead#Diet

    Of course I’m sure PZ could introduce us all to a lot of Cephalod & maybe molluscae generally – marine & terrestrial alike – sex action and, probly (?), inaction here too.. .

    Biology – it ain’t the conservatives or regressives friend. Not that any science really is..

  6. says

    I wonder if at least part of the problem is our confusing language. I think often times we use the word “sex” when we should probably use “gender.” I think of driver’s licenses, as an example. It lists my sex, but it should really be listing my gender. The same goes for many forms, including medical forms!
    The result of this is that the term “sex” is very overloaded and gets misused because people try to use the wrong meaning for the context of the conversation. And some, like Lineham, are probably intentionally misusing the word to sow confusion.

  7. Athywren - not the moon you're looking for says

    To them, the only true measure of a human female is the agility to crap out a brat.

    Of course given that there have been murmurings of functional uterus transplants for a while now, even that might not be something they can cling to much longer.

    At this point I honestly just find it funny when they tell us that “sex is immutable” because to the extent that there’s truth to that, it’s pretty much irrelevant. Of the things that are not presently or theoretically eventually changeable, none of them are things we really care about. Those things we do care about either are or one day will be changeable. “Sex is immutable” is effectively a deepity.

    Also I really enjoy the silliness of the idea that it’s a betrayal of skepticism to accept that biology is more messy, complicated, and mutable than we learn at primary school.

  8. birgerjohansson says

    Athywren @ 9
    There was some bland comedy long ago where Arnold Schwarzenegger became pregnant by (movie science) medical procedure.
    So at least the concept has been in thevpubluc eye for decades.

    Anyway, Arnold could instead reproduce by cloning, like in that other film.

  9. asclepias says

    Hmmm…there’s the bluehead wrasse in the Caribbean. Each male has a harem of females, but if the male is removed, one of the females will change sex to become male. So there’s that.

  10. Ariaflame, BSc, BF, PhD says

    @9 Last I saw, I think it was 71 completed. Most recent I saw was a mother donating to her daughter. They’re only temporary though, estimated 5 years.

  11. says

    In some fish species, the female lays the eggs somewhere, and the male comes along and sprays sperm all over everything.
    I suspect this is the kind of simplicity these guys are looking for in their sex lives.

  12. moonslicer says

    I’m old and tired and well past my sell-by date, and as far as I’m concerned complicated arguments make things too complicated. I simply don’t need them. There’s always a double standard at work: if you fit the norm, what you are is taken for granted. If you don’t fit the norm, for some reason you have to prove you are what you are.

    And the ones you have to prove it to are never going to be convinced by any sort of evidence because they don’t want to be convinced. You’re kind of wasting your time.

    I prove what I am in the same way everybody else does: I get out and live my life. I believe my experience matches that of most, if not all, transgender people. Your average human being doesn’t really care what we are. OK, we’re kind of strange, but as long as we’re not stepping on their toes, they’re OK with us.

    We have to remember, too, that we’re arguing with people who don’t actually understand what transgender people are. I often compare the situation to the “debate” about evolution. The anti-evolutionists quite often don’t understand what evolution is. Which is why you can throw all the evidence you like at them and you get nowhere with them.

    What our opponents routinely fail to comprehend is the notion of gender identity, which is a different thing altogether from gender. As long as they fail to understand that, arguing with them about gender, sex, what-have-you, is pointless.

    They go on and on about sex-denialists, e.g., when all of them are transgender denialists. You wonder just how long you have to exist before people accept that you exist.

  13. euclide says

    @8 Since in a lot of languages we still have difficulties with the mass/weight difference, I’m not that hopeful for sex/genre and anyway, the bigots don’t care.

    They don’t even really care about the whole trans issue, they just want/need a minority out group they can be mean with. Black people, Jews and gays are mostly out limit.

    The trans community is smaller and was in the closet for a long time. That’s the perfect target

  14. kome says

    The intolerance for any aspect of life to be nuanced or complex or more difficult than we teach in kindergarten is fucking baffling. The universe in all its majesty is a huge bundle of mysteries, and these transphobic pieces of shit think they’ve got 100% of the answers before they’ve finished learning to color within the lines correctly.

  15. Akira MacKenzie says

    “Sex denialist” and the TERF battlecry of “Sex is real” sounds suspiciously like certain white supremacist phrases. Just replace “sex” with “race” et voilá!

  16. moarscienceplz says

    PZ Myers
    Betrayer of Skepticism
    Look on my works ye mighty and despair!

  17. says

    Of course “dogma” would come up but that’s just a randomly picked negative characterization for things they don’t like involving any dense information. It’s negative symbol under negative symbol. Being an atheist makes this one visible.

  18. says

    Of potential interest, I tripped up someone who was trying to portray CRT as religion on nextdoor. I notes that I was surprised that they would try a pejorative use of religion and that I saw enough conflation of religion and bad behavior in the atheist community. They still tried but I think I had an effect.

  19. specialffrog says

    @euclide: I think your second paragraph needs “for now” on the end.

  20. Tethys says

    I wonder if the people who insist that gender is an immutable binary have ever encountered plants? They can be male, female, both, and some species with separate sexes also have the capacity to produce either pollen or fruiting structures in response to their environment.

    Snails have numerous reproductive strategies that are proof that biological sex isn’t immutable, or binary. There are species of marine snails that routinely change from male to female in the course of their life cycle. Land snails also have some unusual (by mammal standards)options for sexual reproduction.

    Terrestrial pulmonate snails (Stylommatophora) generally are hermaphrodites, they possess a highly developed genital apparatus with female, male and hermaphroditic organs. In this system, the love dart is produced in a special organ, the dart sac (bursa telae).

    source: https://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/love_dart.html

    By number of species, there are far more organisms that have both male and female reproductive anatomy, than species that have separate sexes.

  21. says

    Transphobes’ fixation on “gametes” seems particularly strange given that they are one of the easiest things to change. Like most AMAB people, I was born with no gametes at all. Then, thanks to a bunch of artificial medicine and surgury, I survived early childhood and eventually started producing sperm. And then, thanks to more artificial medicine and surgury, I no longer have any gametes. Have I changed sex? If sex is based solely on gametes, then I’ve changed sex twice.

    But of course, transphobes wouldn’t accept that: they’d just move the goalposts to one of two places, neither of which are biological:
    1)Intelligent Design gametes: transphobes say your “biological sex” is whatever gametes your body is “intended” to produce.
    2)Hypothetical time-travel alternate reality games: To determine your true biological sex, you have to figure out what gametes you would produce in a hypothetical alternate universe where humans can live until puberty without medical intervention and where you were not given healthcare until after puberty.

    It’s pretty clear that neither of these altered definitions of sex are in any way useful or biological. But it’s the lengths they have to go to convince themselves sex is both binary and can’t be changed.


    “Sex denialist” and the TERF battlecry of “Sex is real” sounds suspiciously like certain white supremacist phrases. Just replace “sex” with “race” et voilá!

    I believe that if Thomas Jefferson were alive, he’d be on Fox News saying “All I did was say ‘race is real’ and now the Woke CRT Marxists are calling me a ‘slave-owner’ and a ‘rapist!'”

  22. rietpluim says

    The problem is that nobody thinks of themselves as being extremist. No racist ever called themselves racist, no sexist ever called themselves sexist, no trans hater ever called themselves trans hater. They think of themselves as realists.

    But “I am no trans hater, there really are only two genders!” is just as stupid as “I am no racist, black people really are lazy!” The real realist’s position is not determined by how well established in reality one thinks their beliefs are, but by the willingness to challenge one’s own beliefs when they conflict with reality.

    Most of us grew up believing in the gender binary I suppose, simply because it is the dominating idea in Western society. But we’ve learned better. They could do too. They just don’t want to. Their appeal to “reality” is just a lame excuse.

  23. Peter Hopkins says

    Saw this discussion unfold on twitter, it always goes the same way…
    “You say ‘sex is socially constructed’? That means you deny sex!”
    “That’s not what I said at all”
    “Okay, explain how this [system I have defined as having only two categories] has more than two categories?”
    Bonus points if they follow up with something about ‘size of gametes’ or by saying something like ‘it’s a strict binary, aside from the outliers’.

  24. Pierce R. Butler says

    These big (~3″) brown hairy-legged spiders keep showing up in my house, often waiting for hours in a given location (always head downward, why is that?) before disappearing and reappearing at random. I consider them rather ornamental.

    Dunno anything about their sex lives, if any, but henceforth I will call them all “wallflower spiders”, and mean it as a compliment.

  25. lumipuna says

    At first I read “wallflower spiders” as “wallflower spinsters”, which would be highly appropriate I guess.

  26. unclefrogy says

    the problem for the “religious” is they do not seem to be able to accept any reality that contradicts what their beliefs are (which are by definition socially derived) any thing that is outside is evil, and sinful, regardless of how common such behavior is generally. They want sex to be primarily about reproduction and anything sex which is not about reproduction as they define it is evil. Now the favorite target of the hour is the transgender, though they still go after same sex attraction but they have more or less lost that one. When the homosexual population was mostly closeted the main target was sex out side of marriage. They can disapprove of that as much as they want but that one is also truly lost to them. All this behavior has always been common across cultures and societies it has not always been condemned sometimes it was even tolerated. If you push them long enough and hard enough they will advocate some form of “The Final Solution” to all of this immorality because that is the root of their argument total control of everything and everyone to force to comply with what they think, no other thoughts are permitted because they are sinful .
    that is what it looks like to me.