The strange sex lives of Aussie redback spiders and their NZ katipō cousins

Embargoed until: Publicly released: 2026-08-12 09:01

Australia; New Zealand; International

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While mating, the male Australian redback spider somersaults onto the fangs of the female (who eats him), making for a longer encounter and chances of babies—but the related NZ katipō doesn’t do this. Researchers bred the two spiders together to see whether babies inherited the somersault. About half did, suggesting DNA on the X chromosome drives the behaviour, and that the katipō has lost this DNA. However, inheritance of another behaviour—the male tightening his body after somersaulting to delay death from female bites—was more complex. The researchers say it's surprising that the self-sacrificing somersault can be driven by such simple genetics.