Venus in Silks

Pisaurina mira courtship. Photo by Alissa Anderson.

The prospective groom carefully drapes a silken veil across his chosen mate’s head, then wraps four of her eight legs, her chelicerae, and her pedipalps. It turns out human brides aren’t the only ones to wear white.

Spider courtship is a complicated and fascinating affair. Various species in the Northeast use at least three different types of silk bonds in their mating rituals. For the first type, the male attaches his silk to the ground as a sort of tether and then ties it to the female’s body or legs. This behavior is common among some wolf spiders, nursery web spiders, and crab spiders. A second type involves the male’s ringing the female with his silk and binding her legs to her body. Some of our nursery web spiders use this tactic. For the third type, the male wraps the female while both partners hang from silk threads, inspiring one blogger and arachnophile to coin the phrase “the centimeters-high club.” Some of our native nursery web spiders, including the common Pisaurina mira, are members of the club.

Scientists use the term “bridal veils” to refer to such behavior and have come up with many hypotheses to explain why male spiders might resort to such tactics. Spider courtship is notoriously risky for the male, so it’s possible the silk is meant to restrain the female, or at least slow her down, making it less likely the male will become dinner instead of a date. Physically immobilizing the female might also make mating easier for the male, who is often much smaller than his partner. Alternatively, the male’s silk may be chemically or physically stimulating. It could provide information about the male, such as his species or quality as a potential mate. It could also leave “I’m spoken for!” indicators to warn off rival males the female might encounter later.

Mariana Trillo, a researcher at the Clemente Estable Biological Research Institute in Uruguay, has been observing wandering spiders that tie silken nuptial knots. She noticed that the females eat the silk bonds after mating. “If she eats the silk, it could be a kind of nuptial gift for spiders,” said Trillo.


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