In this paper, the microstructure of chafer cuticle is observed with a scanning electron microscope (SEM). The observation shows that the insect cuticle is a kind of biocomposite with hybrid structural characteristic of various chitin fibers embedded in protein matrix. The reinforced chitin fibers vary in size, shape, property and distribution, which are related to their location in the cuticle. Near the surface of the cuticle, the chitin fibers are smaller, stiffer, more circular, and the orientations of the chitin-fiber plies are various. A kind of helicoidal layup is found. The dependence of fracture strength on the fiber diameter and the dependence of fracture toughness on the parameters related to helicoidal layup are experimentally investigated. It shows that the smaller fiber and the helicoidal layup endow the surface of the cuticle with higher fracture strength and toughness.