Among the most interesting forms of the family are the two species of the genus _Nocticola_, recently discovered by M. Simon in caves in the Philippine Islands.[160] They are amongst the smallest of the Orthoptera, the male being scarcely ⅛ of an inch long. In the larval state of _N. simoni_ the ocular organs exist as three ocelli, or facets, on each side of the head, and in the perfect state the number is increased somewhat, as shown in Fig. 127, A_{2}. In the second species of the genus the female is quite blind (the male being still undiscovered). The fenestræ in _Nocticola_ are absent; the tegmina and wings are totally wanting in the female (Fig. 127, B), but are present in a very peculiar condition in the male (Fig. 127, A_{1}). There are other anomalies in the structure of these cavernicolous Insects, the cerci being apparently of peculiar structure, and the spines of the legs more hair-like than usual. The condition of the eyes is remarkable; the peculiarity in their development is worthy of study. [Illustration: FIG. 128.—_Corydia petiveriana_, with tegmina extended, A; closed, B.] To those who are acquainted with Blattidae only through our domestic "black beetle" it may seem absurd to talk of elegance in connexion with cockroaches. Yet there are numerous forms in which grace and beauty are attained, and some exhibit peculiarities of ornamentation that are worthy of attention. _Corydia petiveriana_ (Fig. 128) is a common cockroach in East India. It has an effective system of coloration, the under wings and the sides of the body being vividly coloured with orange yellow; when the tegmina are closed the upper surface of the body is of a velvet-black colour, with cream-coloured marks; these spots are different {234}on the two tegmina, as shown in Fig. 128, A, but are so arranged that when the tegmina are closed (Fig. 128, B) a symmetrical pattern is produced by the combination of the marks of the two differently spotted tegmina. It is very curious to notice the great difference in the colour of the part of the right tegmen that is overlapped by the edge of the left one; this part of the tegmen being coloured orange yellow in harmony with the wings. The result of the remarkable differentiation of the colours of the two tegmina may be summarised by saying that on the right one the colour of a part is abruptly contrasted with that of the rest of the organ, so as to share the system of coloration of the under-wings and body, while the corresponding part of the other tegmen is very different, and completes the system of symmetrical ornamentation of the upper surface.