Females of the orb-weaving spider Argiope bruennichi are very cannibalistic and regularly terminate copulations by aggressively attacking the male. Few males survive mating and they escape only if they mate no longer than 8 seconds on average. We speculated that the brief copulations of surviving males will not result in complete fertilization of all of a female's eggs and that multiple mating is necessary to compensate for that. Surprisingly, we found no difference in the proportion of hatched young in clutches of females that were experimentally assigned to mate once or twice. Even females that mated with one male for less than 10 seconds produced clutches with hatching rates no different than treatments with two matings. The question remains why males risk their lives by prolonging copulation duration. Possible causes and functions in the context of sexual selection are discussed.