Sex Tips From Spiders

A male wolf spider (Schizocosa uetzi) with ornamental pigmentation. Cornell University researcher Eileen Hebets found that female wolf spiders encountering a courting male preferred to mate with ones who looked like males they had met when they were youngsters. Unfamiliar-looking males were more likely to be attacked or eaten.(National Academy of Sciences)
Mate or meal: A female wolf spider's first exposure to courting could mean life or death for her later lovers.

In many animal species - including humans - adolescent females are often exposed to the courtship advances of older males, observed researcher Eileen A. Hebets of Cornell University. Those experiences can affect how she reacts to similar advances when she grows up.

In the case of wolf spiders, Hebets found that immature females encountering a courting male preferred when they reached mating age to mate with males who looked like those they had met as youngsters. And, they were more likely to attack and eat unfamiliar males than to mate with them, Hebets found.

While several studies have shown that such youthful experiences affect adult mating behavior in larger animals, this is the first to show the effect in invertebrates - animals without backbones - said Hebets, who is shortly to join the faculty at the University of California, Berkeley.

Her findings are reported in this week's online issue of Proceedings of the National Academy of Sciences.

"I think everyone is surprised" by the finding, she said. People generally think of spiders as simple creatures and don't expect them to learn and remember.

From the scientific viewpoint, she said, the behavior is interesting because it shows a way females make a mate choice and can drive the evolution of male traits.

Learning how mate choices are developed may shed light on why larger species and even people tend to prefer one type of mate over another, she said.

In Hebets' experiment, she placed immature female spiders in a plastic box on a paper that contained the scent of a mature female spider. Then she introduced a male spider, which sensed the scent and went into its ritual mating movements, observed by the younger female.

Male wolf spiders have either black or brown forelegs. Hebets accented this with nail polish - Cover Girl midnight metal or bronze ice - exposing 81 females to either black- or brown-legged males.

Weeks later, after the females had a final molt and were old enough to mate, Hebets again placed them with males.

When females were placed with a male with the same leg color they had seen as youngsters they mated between 40 percent and 50 percent of the time and ignored the others.

But when they were placed with a male of the opposite leg color they only mated about 10 percent of the time, and they attacked and ate the males twice to three times as often.

It's not unheard of for female wolf spiders to cannibalize their mates, Hebets said, but it usually occurs after mating. In the experiment they attacked before mating, almost as though they didn't recognize the different colored males as the same species, Hebets said. They did not attack the males with the familiar leg color.

By Randolph E. Schmid