This process is termed the retinaculum, and serves, in conjunction with the frenulum, to lock the wings together during flight.
In many of the Lepidoptera both frenulum and retinaculum are entirely wanting.
The retinaculum is not correctly represented in this figure, it arises from the anterior side of the sub-costal nervure.
Most, however, have four, the leaf stomach or psalterium being intercalated between the retinaculum and the abomasum.
retinaculum ret·i·nac·u·lum (rět'n-āk'yə-ləm)
n. pl. ret·i·nac·u·la (-lə)
A band or bandlike structure that holds an organ or a part in place.