Why might female red-back spiders consume males during mating?

In the context of reproductive behaviour, the practice of females consuming males during mating is known as sexual cannibalism. In the case of the redback spider, this behavior occurs in approximately 65 percent of matings.1

From an evolutionary perspective, this behavior provides several potential benefits:

• Nutritional Investment: Consuming the male provides the female with additional energy and nutrients, which can be invested into producing heavier egg cases and more numerous offspring.1
• Increased Reproductive Success: For the male, who often faces a high probability of dying without ever mating, the sacrifice can be an evolutionary strategy. By allowing himself to be eaten, he may ensure the female produces hardier or more numerous offspring, thereby increasing the chances that his genes are passed on.1
• Prolonged Mating: The act of being eaten can facilitate longer mating sessions, which may allow for more effective sperm transfer.1
• Reduced Sperm Competition: Consuming the male may discourage the female from mating again for a period, reducing the likelihood that subsequent males will fertilize her eggs.1