Sphragis

In many species, mating is preceded by complex courtship rituals, in which females have a choice of mate. However, the male sometimes places a plug or “chastity belt” on the female after mating, limiting her ability to choose other mates. This structure is called a sphragis, from the Greek word for “seal.” These sphragis devices can range from a simple plug secreted by a male into female’s mating tube at the end of copulation, to elaborate shell-shaped structures attached to the outside of the female’s abdomen that prevent the male’s claspers from holding onto the female and positioning his genitalia for mating.

In African Acraeabutterflies, a male can grab a flying female in the air and take her down onto the ground to mate with her. Other males might later attempt a similar strategy with the same female, but they will not be able to attach themselves to the female’s abdomen, whose mating tube is blocked by a waxy plug, and pairing will not take place. In the Holarctic genus of...