That might have been because the males always tied up the females and so were never eaten. “I have never seen a male not wrap the female,” in nature, Ms. Anderson said. She and her adviser, Eileen A. Hebets decided to run some experiments.

As they reported in Biology Letters last month, they used dental silicone to block some male spiders’ spinnerets — where the silk comes from. They left other males free to execute the usual plan. As expected, the males that couldn’t produce silk were eaten much more often than the other males.

Males with longer legs were also more successful at surviving, showing that size is important if you are in a species in which courtship makes mixed martial arts look like a Texas two-step.

Ms. Anderson, whose work on the spiders is part of her doctoral research, wants to determine if there is a benefit for the females as well as the males in this kind of mating.

The males who are able to wrap the females’ legs have more successful copulations, as measured by the number of insertions of the pedipalp, which delivers sperm to the female. And if the result is that the females who have been wrapped have more eggs, that could mean that both sexes benefit and the behavior is, at least in evolutionary terms, mutually beneficial.