When you're a male Cyrtophora citricola spider, a first date goes as follows:
You happen upon a lady's web. She plucks at the silk, strumming a seductive tune as she approaches. You strum back in response. The two of you copulate. When it's over, she lifts you to her mouth, holding your body to her lips.
And then she eats you.
So a male spider's first date quickly becomes his last. Ever. But that's okay. Male spiders know their place. They understand that their sole purpose is to fertilize a lady's eggs. So they've evolved to make the best of a bad situation. They choose the best lady they can, someone who will appreciate their unique flavor and — more importantly — ensure that their genes live on in her young.
"All they can do is just try to get as much fitness out of their one copulation as they can," said Eric Yip, a behavioral ecologist and the author of a new study in the journal PLOS ONE describing this behavior.
Yip started researching Cyrtophora citricola as a post-doctoral student at Ben Gurion University in Israel (he's now at Penn State). They are members of the orb-weaving spider family, characterized by large female spiders who build the wheel-shaped webs you're used to seeing in your garden. Many orb weavers are cannibalistic — females will attempt to eat their mates as soon as sex is over.
"He’s really no more use to her," Yip said. Except as "a nice protein-rich meal."
Most kinds of male orb weavers are often — if not usually — able to avoid these deadly dinner dates. But among a few species, including Cyrtophora citricola, the dudes lost that particular evolutionary battle a long time ago. They're about a quarter of the size of their female counterparts, and really bad at running away; guys get eaten after sex 80 percent of the time. It's apparently not a bad evolutionary strategy: though they're native to the Mediterranean, the spiders have spread to become an invasive species on almost every continent.
In most of the animal world, male members of a species will indiscriminately attempt to mate with as many females as possible (thus increasing the likelihood that their genes will live on in the next generation). But Yip noticed that male citricolas took a different tack. Given just a single chance to reproduce, they appear to be particularly choosy about who the moms of their only children might be. They prefer younger, larger females — who are generally healthier and able to lay more eggs. They also prefer females that haven't had sex before, since that means they won't have to compete with another guy's sperm.
In many cases, the male spiders will play hard to get when they land on a female's web. If they're not sufficiently impressed by her, they'll run off in search of someone else.
This strategy works because citricolas live in colonies, giving males plenty of opportunity to scout out a potential mate. And guy spiders get other benefits from it as well: According to Yip, the process of cannibalizing their mates seems to make females less likely to copulate with another male, and it allows males to transfer more of their sperm to the female. It's a win-win situation.
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