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The story
During mating, male redback spiders flip their own bodies around and offer up their abdomen to the female’s fangs, letting themselves be eaten right there. After Nazology published an article on this behavior, 5ch reacted with everything from astonishment at research showing that cannibalized males have a median mating duration of 25 minutes versus just 11 minutes for males that aren’t eaten, to a personal account of encountering one in a Kawasaki apartment.
Posts also focused on explaining the logic behind why males “choose” to be eaten, with comments like “the odds of meeting another female if you flee are low” and “getting eaten means longer mating time, which works in your favor.”
The Redback Spider’s Bizarre “Eaten by the Female After Mating” Behavior Turns Out to Be Genetically Surprisingly Simple
Living things generally try to flee when danger approaches.
But the male Australian redback spider (Latrodectus hasselti) does the opposite: during mating, it flips its own body around, offers its abdomen to the female’s fangs, and afterward simply lets itself be eaten by her.
Source: nazology.kusuguru.co.jp / Read the original article here
What people said
That's only Japanese mantises
Apparently Chinese mantises have the male and female fight it out, and the male sometimes wins
Did they evolve this way to boost genetic diversity instead of just passing on the same genes?
Is it 100% for these spiders, though?
Wish they could slowly merge together like anglerfish do lol
But yeah, right when the post-nut clarity hits and you realize you're being eaten, you'd probably snap out of it and scream
Guess the ones who felt that way got weeded out by natural selection
You get 'eaten' by your wife after marriage
One showed up in my room
There was a neighborhood flyer going around like "Report any redback spider sightings!"
Turns out it was your house lol
Female redback spider: "I loved him so much I just had to eat him…"
If you happen to be there when they hatch, they'll even eat their own siblings
Come on, the source site should proofread this stuff before publishing
Husbands are just ATMs
That's the law of nature
That's literally you guys
>> During mating, the female mainly bites the part of the abdomen behind this constriction. Past experiments confirmed that males given an artificial wound in that same spot behind the constriction survived longer.
In the animal kingdom it's nutrients, in human society it's money — either way, women are devouring value out of men
That's just obvious
Insects don't raise or teach their young, so once a male's passed on his genes he's useless anyway
So him becoming nutrition is just a net plus for the species' survival
That footage of one still desperately mating even after losing its head was wild.
the male has to go off and "fight" or protect the family after mating
Redback spiders probably don't have to bother with any of that
I don't get what you're saying, is that even Japanese?
and the hoopoe, which lays extra eggs just to feed its earlier-hatched chicks
nature is terrifying
but now they're just everywhere, and you don't even need to report it anymore
Getting eaten extends mating time, which works in your favor
Getting eaten raises the odds the female rejects the next male
It becomes nutrition for the kids
Yeah, I'd pick getting eaten too
Background and Key Points
The redback spider (Latrodectus hasselti) is a highly venomous species native to Australia that has established itself in parts of Japan since it was first discovered in Osaka in 1995, likely arriving via international cargo. Because it’s an invasive species with medically significant venom, Japanese municipalities historically ran public sighting-report campaigns, which is the backdrop behind the poster’s story of a neighborhood flyer asking residents to report redbacks — not realizing the spider was already living in their own room. Sexual cannibalism itself isn’t unique to this species (mantises came up repeatedly in the thread), but redback males are unusual in actively facilitating their own death: flipping their abdomen toward the female’s fangs mid-copulation rather than being caught or overpowered.
The thread didn’t split over whether this happens, but over how to interpret it — is offering yourself up “obvious” adaptive logic (better odds of siring offspring given males rarely get a second chance, so become nutrition for your own young) or is it “just sad,” a fate to pity even if evolutionarily rational. That divide mapped onto a lighter argument about whether a rational human would ever “choose” this trade-off, versus panicking mid-act once realizing what’s happening.
What the thread never addressed is the actual mechanism, despite citing it: the constriction behind which females bite is a real, described anatomical feature, but no poster asked why males evolved a body part that makes self-sacrifice physically easier — that’s an active area of research, not settled science. Readers may also assume this behavior is universal to the species, when field data cited in the thread shows the roughly 80% of males that die before ever mating outnumber those that get a cannibalized — or any — copulation at all.
*This article is excerpted and summarized from the 5ch (Science News+) thread “[Nazology] The Redback Spider’s Bizarre “Eaten by the Female After Mating” Behavior Turns Out to Be Genetically Surprisingly Simple.”
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