Ultrastructure of a scent scale organ with pressure discharge in male Caligo eurilochus brasiliensis (Fldr.) (Lepidoptera/ Brassolidae).

The abdominal scent apparatus of male Caligo eurilochus was examined at different ages by light, scanning and transmission electron microscopy. The glandular epithelium is covered with specialized scales and forms a pad on each side of the 4th to 6th abdominal segments. The pads are surrounded by smooth, elastic cuticle and can protrude toward the opposite hind wing hair pencil. The scales have a poreless cuticle with a fibrillar texture. They are impregnated by an oily, slowly volatile substance. The scales are elongated toward the base, forming hoods over the long cone-shaped sockets. The scale pedicel is anchored tension-free by rootlets in the central socket base. The slightly asymmetric cuticular sockets are very elastic, due to their high water content. They are stabilized by internal epicuticular rods. The release of the secretions from the cell and a possibly active microvillar transport is discussed. Different secretions are found in the space between the microvillar surface of the gland cell and the socket floor. They are probably discharged from the supraglandular space into the scale lumen by means of pressure and bending of the sockets. A flowback might be prevented by capillary effect of a "ball" of vesicles, which lies exactly above the outlet of the scale pedicel.