The Generalized Feeding Apparatus of Cockroaches: A Model for Biting and Chewing Insects

Abstract

The morphology, musculature, and function of the feeding apparatus of cockroaches is described in detail and compared with other insects with biting and chewing mouthparts. The mouthparts of cockroaches represent, in most cases, the ancestral condition for winged and neopteran insects. Their head capsule is flattened in a posterior-anterior direction and very similar among the studied species. The right mandible is very constant in shape, while the number of distal incisivi in left mandibles varies among species. With the exception of Tivia sp. (Corydiidae), primary mandibular adductor of the mandible has eight distinct compartments in all studied roaches, for which functional cross section and volume are provided. In all these specimens, the left adductor is smaller than the right one. Bite forces and muscle properties are discussed for Periplaneta americana. The maxilla, labium, and hypopharynx are also highly similar among cockroaches and close to the pterygotan ground plan. The same also applies to the associated musculature for which we also provide functional and kinematic considerations. Cockroaches salivate food outside the mouth cavity before cutting it with the mandibles. The maxillae transport food into the cibarium where the hypopharynx is involved in transporting it between the grinding mandibular molae. The crushed food is sucked into the pharynx via dilation. During the feeding process, most mouthparts exhibit highly concerted activities. This process generally follows the ground pattern for insects with biting and chewing mouthparts, although some salivation processes may differ.