Spider Courtship

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Spider Courtship

Marfa Public Radio

Broadcast on October 14, 2010

Lynx spider courtship

Lynx spiders courting. (Photo by Cathryn Hoyt)

Tarantula on the prowl

A tarantula on the prowl for a mate. (Photo by Cathryn Hoyt)

By Roseland Klein

Finding a mate can be difficult for anyone. But imagine trying to win over a hungry, short-sighted cannibal, a few times your size. This is the challenge for many male spiders, for whom courtship can be fraught with peril. How do male spiders demonstrate they’re mates, not meals? And is there some advantage to being eaten?

Spider courtship begins peacefully, with the male spinning a napkin-like web, onto which he drops his sperm. He then takes up the sperm in his pedipalps. These diminutive appendages near a spider’s mouth are normally used for eating. But in males, the tips are outfitted with bulbous structures for holding sperm and inserting it into females. With pedipalps loaded, a male spider begins looking for love, which he finds by following pheromone trails that receptive females slather onto their webs.

Here’s where courtship can become a perilous affair. Spiders have different strategies when it comes to approaching and convincing potential mates that they’re not prey.

Brown recluses, for example, put on a show. A male brown recluse first cautiously tweaks and taps a female’s web for awhile to signal his interest in breeding. Then he struts his stuff in a bizarre ballet, waving his pedipalps and legs and striking unusual poses. If the female finds his performance satisfactory, they proceed to mate as spiders do, with the male inserting his sperm-laden pedipalps into the female’s genital openings.

Black widows take a similar approach, but with less fanfare. The male strikes and plucks a female’s web to alert her of his intentions. He also strategically severs strands of her web, reducing her potential routes of escape and attack. She may reject him by charging at him, in which case he’ll try to flee. But if she accepts, he gingerly approaches and begins caressing her legs and abdomen. Then, they mate.

At this point, black widows only occasionally live up to their name, at least among species in the U.S. In fact, the widely held belief that female black widows eat males immediately after mating is a misconception, particularly with the species common to our region.

However, after mating, males don’t have much purpose in life and don’t live long. So sometimes they’ll linger on a female’s web to offer themselves as a post-nuptial meal. By making this sacrifice, they give their mate a nutritional boost and thereby posthumously improve the chances of their reproductive success.

Then there are tarantulas, whose big fuzzy bodies you’ll often see crossing our highways in summer and fall. These wandering hordes are males seeking mates. Female tarantulas are homebodies, usually spending their entire lives in the same burrow. They leave it up to males to find them. After waiting as long as 10 years to reach sexual maturity, nomadic males have only a few months to reproduce, and their quest for a mate can take them miles across the desert.

When a male tarantula finally locates a receptive female’s burrow, he announces his presence by drumming his legs and pedipalps on the web at her burrow entrance. She may emerge with a violent lunge, and if her admirer doesn’t make a hasty retreat, he may be eaten.

But if she accepts his advances, she’ll rise up and spread her fangs. The male then hooks her fangs onto little spurs on his legs to mate. The female sometimes decides she requires her partner’s protein after mating, and the male’s life ends with being eaten. As with black widows though, a male who becomes a meal is merely helping his partner and increasing his offspring’s odds of survival.

Have a question or comment about this episode? Contact Nature Notes Coordinator Megan Wilde at mwilde@cdri.org. Or discuss this episode on Nature Notes’ Facebook page. This episode originally aired on October 14, 2010.

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