Fig. 5

a Structure of arthropod cuticle showing the four primary layers and fine structure of the surface. Also shown are vertical channels—dermal gland ducts extending from the epidermis and secreting an as yet unknown substance and pore/wax canals which carry lipids from the epidermis to the epicuticle. After Hadley (1986). b Spiracles of a cockroach, shown closed (top) and open (bottom). After Bell and Adiyodi (1982)