Some four-winged insect orders, such as the Lepidoptera, have developed a wide variety of morphological wing coupling mechanisms in the imago which render these taxa as "functionally dipterous" for ef
Oiketicus spp. (family Psychidae). The frenulum can be seen at the top of the rear wing, which hooks onto the retinaculum, seen here as a small brush on the front wing, so that the wings travel together during flight. Magnification: 10x