[Illustration: FIG. 223.—Under-surface of _Embia_ sp. Andalusia.] The simple antennae are formed of numerous joints, probably varying in number from about fifteen to twenty-four. The mouth is mandibulate. Chatin states[277] that the pieces homologous with those of a maxilla can be detected in the mandible of _Embia_. The labium is divided. The legs are inserted at the sides of the body, the coxae are widely separated (Fig. 223), the hind pair being, however, more approximate than the others. The abdomen is simple and cylindrical, consisting of ten segments, the last of which bears a pair of biarticulate cerci. In the male sex there is a slight asymmetry of these cerci and of the terminal segment. The thorax is remarkable on account of the equal development of the meso- and meta-thorax and their elongation in comparison to the prothorax. When they bear wings there is no modification or combination of the segments for the purposes of flight, the condition of these parts being, even then, that of wingless Insects; so that the Embiidae that have wings may be described as apterous-like Insects provided with two pairs of inefficient wings. The wings are inserted on a small space at the front part of each of the segments to which they are attached. The legs have three-jointed tarsi, and are destitute of a terminal appendage between the claws. [Illustration: FIG. 224.—Anterior wing of _Oligotoma saundersii_: A, the wing; B, outline of the wing, showing nervures. (After Wood-Mason.) 1, Costal; 2, subcostal; 3, radial; 4, discoidal; 5, anal nervure.] The wings in Embiidae are very peculiar; they are extremely {353}flimsy, and the nervures are ill-developed; stripes of a darker brownish colour alternate with pallid spaces. We figure the anterior wing of _Oligotoma saundersii_, after Wood-Mason; but should remark that the neuration is really less definite than is shown in these figures; the lower one represents Wood-Mason's interpretation of the nervures. He considers[278] that the brown bands "mark the original courses of veins which have long since disappeared." A similar view is taken by Redtenbacher,[279] but at present it rests on no positive evidence. One of the most curious features of the external structure is the complex condition of the thoracic sternal sclerites. These are shown in Fig. 223, representing the under-surface of an _Embia_ of uncertain species recently brought by Mr. Bateson from Andalusia.