The legs are remarkable for the large and numerous spines borne by the tibiae, and frequently also by the femora: the trochanters are distinct and of moderate size; the tarsi are five-jointed, frequently the basal four joints are furnished with a pad beneath; the fifth joint is elongate, bears two claws, and frequently between these a projecting lobe or arolium; this process scarcely exists in the young of _Stilopyga orientalis_, the common cockroach, though it is well developed in the adult. The hind body or abdomen is always large, and its division into rings is very visible, but the exact number of these that can be seen varies according to age, sex, species, and to whether the dorsal or ventral surface be examined. The differences are chiefly due to the retraction and inflexion of the apical segments; the details of the form of these parts differ in nearly every species. It is, however, considered that ten dorsal and ventral plates exist, though the latter are not so easily demonstrated as the former. The basal segment is often much diminished, the first dorsal plate being closely connected with the metanotum, while the first ventral may be still more rudimentary; much variety exists on this point. In the female two of the ventral terminal plates are frequently inflexed, so as to be quite invisible without dissection. From the sides of the tenth segment spring the cerci, flat or compressed processes very various in size, length, and form, usually more or less distinctly jointed. Systematists call the seventh ventral plate of the {224}female the "lamina subgenitalis," or the "lamina subgenitalis spuria," the concealed eighth plate being in this latter case considered the true subgenital plate. In the male this term is applied to the ventral plate of the ninth segment, the corresponding dorsal plate being called the "lamina supra-analis." These terms are much used in the systematic definitions of the genera and larger groups. The males, in addition to the cerci alluded to as common to both sexes, are provided on the hind margin of the lamina subgenitalis with a pair of slender styles. These are wanting in the females, but in the common cockroach the young individuals of that sex are provided, like the male, with these peculiar organs. M. Peytoureau has described[147] the mode of their disappearance, viz. by a series of changes at the ecdyses. Cholodkovsky, who has examined the styles, considers them to be embryologically the homologues of true legs.[148] These styles are said not to be present in any shape in some species—_Ectobia_, _Panesthia_, etc.; this probably refers only to the adults. In some cases a curious condition occurs, inasmuch as one of the two styles is absent, and is replaced by a notch on the right side, thus causing an asymmetry—_Phyllodromia_, _Temnopteryx_, etc.