As generations of biology students have discovered to their morbid delight, the mating behavior of insects can be bizarre. The classic example is lovemaking among praying mantises, where the female has sex with her partner, then eats him for dessert. But the mantis has nothing on its distant cousin, the orb-weaving spider. In this case, though, the male seems to offer himself as a sacrifice, to the point of actually killing himself before the female has a chance to. His heartbeat ceases and he curls up and dies--even before the female can begin attacking him. Theories abound that male self-sacrifice may be a logical extension of the practice employed by many animals, including insects and spiders, of the male bringing a gift of food to encourage the female to mate. Matthias Foellmer of Concordia University in Montreal and Daphne Fairbairn of the University of California, Riverside, believe they have found at least part of the answer. As they explain in a paper in the Proceedings of the Royal Society, other males may fight over access to the female and try to dislodge any male that has an inserted palp. However, the palps of dead males are fixed in an inflated state, making them hard to remove. As a result, dead males may act as plugs to prevent other males from copulating, ensuring that the suicidal male, not a rival, fathers the offspring.