bridle

…a structure known as a bridle, also called a frenulum, a pair of oblique cuticular ridges that extend backward to meet in the midventral line. The bridle supports the protruding worm on the edge of its tube. The metasome is divided into two sections by a pair of parallel ridges…

…or cluster of bristles (frenulum) near the base of the hind wing engages a catch (retinaculum) on the forewing. In some moths and in the skippers and butterflies, the frenulum mechanism has been lost, and the wings are coordinated by the friction of the overlapping areas. In the most…