Male nursery web spiders often woo potential lady-friends with gifts wrapped in silk. Mating may ensue, during which a female unspools the present, expecting to find a tasty treat. But the males can be unscrupulous. Some offerings contain inedible plant seeds or empty insect exoskeletons. …The empty-handed males were mostly unsuccessful at mating. Whereas those with a gift could get the girl. But if the gift was worthless, the females quickly realized the deceit and pushed the copulating males off.

The Scientific American blog post (based on this paper) makes it sound as if the males are the only ones using deception and dirty tricks. But why do the males silk wrap their gifts? Why not just present the females with food?

Females presented with food will often grab the food and run, leaving the males doubly hungry. A wrapped package is harder to steal (the males have a better grip on the silk) and as the females slowly unwrap their potentially delicious presents the males copulate. Thus, the rituals of silken wrapped gifts conceal intricate conflicts over resources and sex. Only among spiders, of course.