Fig. 10. Scanning electron micrographs of the anterior thoracic spiracle after descaling the prothoracic cuticle. (A) Peritrema with dense cuticular filter lamellae. (B) After removal of most of the filter lamellae, the half-opened inner valve lip (IL) and the orifice (O) are visible. (C) Outer layers of the filter meshwork; enlargement of boxed region in A. (D) Transverse section of the base of the anterior lamella revealing that approximately six rows of cuticle processes are connected by anastomoses. Enlargement of boxed region from B.