The cephalic morphology of the American cockroach Periplaneta americana (Blattodea)

The skeleto-muscular system of the head of the American cockroach Periplaneta americana is described in detail. The results are compared with previous partial descriptions of the cephalic morphology of this species and other dictyopterans. The head of Periplaneta is, as in other cockroaches, mostly characterized by plesiomorphies such as the typical orthopteroid mouthparts, the lateral position of the compound eyes, 5-segmented maxillary palps and 3-segmented labial palps, as well as long antennae. Periplaneta shows sexual dimorphism with the compound eyes of the males reaching further ventrally. The epistomal ridge is medially interrupted so that the frons and the clypeus are confluent. The cephalic musculature is typical for a polyneopteran insect and includes 59 muscles. Potential apomorphies for Blattodea in the cephalic area include the absence of the median ocellus, the bipartite condition of M. verticopharyngealis (0ph1) and of M. hypopharyngosalivaris (0hy12), and the presence of oesotendons. The lacinula, a subapical lobelet on the lacinia, is present in almost all studied blattodeans but its potential homology to the dentisetae of Palaeoptera or the lamellae of apterygotes cannot be addressed at the moment. A "perforate" tentorium, a membranous postmola, and a lacinia that fits into the concave mesal wall of the galea are confirmed as autapomorphies of Dictyoptera