Guys, the next time you’re trying to work up the nerve to approach a lady in a bar, just be grateful she won’t eat you before you get a chance to say hello. The male web-building spider isn’t so lucky: To start his courtship ritual, he must venture onto a female spider’s web, running the risk that she will mistake him for trapped prey and gobble him up in an ill-advised bout of what scientists call “precopulatory cannibalism.” In an attempt to avoid this fate, the first thing male spiders do when they set foot on a female’s web is quickly rock back and forth, sending distinctive “courtship vibrations” across the strands of silk. Now, a new study confirms that these shudders might mean the difference between life and death. Female Argiope keyserlingi spiders (like the one pictured above) were much slower to eat a trapped cricket  when researchers played a recording of a male’s courtship shudder than when they played white noise or let them feast in silence, the team reports today in Scientific Reports. This suggests that the shudder tells the female to take her time reacting to a vibration in her web, giving the male spider a chance to get close enough to prove he’s not a meal. Still, there’s no room for dilly-dallying—eventually, the females ate even the supposedly shuddering crickets, suggesting that males have a limited time in which to make their move.