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Meet the Spider Species Whose Males Irreversibly Mutilate the Genitals of Their Mates

He breaks off something called her "scapus" to keep competing sperm from getting in.

by Mike Pearl
Nov 7 2015, 12:41am

Larinia argiopiformis, similar in appearance to Larinia jeskovi.

Larinia argiopiformis, similar in appearance to Larinia jeskovi. Photo via Wikimedia Commons

If you didn't receive your November issue of Current Biology yet, you're missing out on a big, horrible story about sexual violence in spiders. Researchers at the University of Greifswald in Germany have discovered that the males of a particular species of orb weaver have a devious strategy for keeping females from mating again after they finish with them: They destroy a crucial part of their genitalia.

Read: Have Scientists Learned Anything from Giving Drugs to Spiders?

According to the paper "Securing Paternity by Mutilating Female Genitalia in Spiders" by various members of the University of Greifswald's zoology department, the species in question is Larinia jeskovi, a type of orb weaver.

Larina jeskovi spider sperm have a tough time accessing females and their eggs, so after mating, males have tricks up their sleeves for keeping other sperm from getting into the female. According to the paper, they insert a genital plug, they stand around scaring off other males, and they make females less attractive by transferring "manipulative substances" onto them. In contrast, the authors call directly damaging the female's genitals a "drastic" measure.

Outside the female's genital opening there is a protruding shaft called a scapus, and it's required in order for the male to latch on during copulation. Researchers found that something occurred during mating in which the male's genitals broke off the scapus, making it impossible for the female to mate again.

You're probably feeling like Werner Herzog right now, vis a vis nature:

But it's not just a handful of asshole spiders who do this; it appears to be standard. The report found that among spiders studied in the field, all of the females were without a scapus at the conclusion of the mating season.

However, before anyone goes on a spider-stomping spree, and targets the males of this particular species for being abusive and possessive toward their mates, it's important to note that this is just the one species where the behavior has been documented.

They suspect that this act of aggression might be common among other species of spiders with similar interlocking genital structures, but many of the genital-mutilating species just haven't been discovered yet.

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