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 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.
Many other members of the Blattidae have an elegant appearance, and depart more or less from their fellows in structural characters, with the result of adding to their graceful appearance; in such cases, so far as at present known, these Insects are brightly coloured. Thus Hypnorna amoena (Fig. 129) has the antennae banded in white, black, and red, while the overlapping part of the tegmina is arranged so as to bring the line of junction between them nearly straight along the middle line of the body, and thus produce a more symmetrical appearance than we find in other cockroaches. The head in this Insect is not so concealed as usual, and this undoubtedly adds somewhat to the effective appearance of this cockroach. This visibility of the front of the head in Hypnorna is not, as would be supposed, owing to its being less inflexed than usual. On the contrary, the head is quite as strongly inflexed as it is in other Blattidae, but the part just at the front of the thorax is unusually elongate, so that the eyes are exposed and the Insect has a larger field of vision. This interesting Insect belongs to the tribe Oxyhaloides [Plectopterinae Sauss.], in which group the most highly developed folded wings occur.
Fig. 129.—Hypnorna amoena. Central America. Tribe Oxyhaloides. (After de Saussure.)
The wingless forms never exhibit the grace and elegance possessed by some of the more active of the winged Blattidae. One of them, Gromphadorhina portentosa, found in Madagascar (Fig. 130), is a very robust Insect, and attains a length of 78 millim.—somewhat more than 3 inches. This Insect has projections on the thorax that remind us of the horns that exist in some of the Lamellicorn beetles.
Little has been yet written as to the resemblances of Blattidae to other species of their own family, or to other creatures, but it is probable that such similarities will be found to prevail to a considerable extent. W. A. Forbes has called attention[[161]] to the larva of a Blattid from Brazil as being remarkable for its superficial resemblance to an Isopod crustacean. Some of the wingless forms have a great resemblance to the small rolling-up Myriapods of the group Glomerides; Pseudoglomeris fornicata, of which we figure the female (Fig. 131), has received its name from this resemblance. The females of the S. African genus Derocalymma possess this Glomerid appearance, and have a peculiar structure of the prothorax, admitting of a more complete protection of the head. Brunner states that the wingless kinds of Derocalymma roll themselves up like wood-lice. In many of the forms of this tribe—Perisphaeriides—the males are winged, though the females are so like Myriapods. According to de Saussure[[162]] the gigantic Megaloblatta rufipes bears an extreme resemblance in appearance to the large cockroaches of the genus Blabera.
Fig. 130.—Gromphadorhina portentosa, × ⅔. Tribe Perisphaeriides. (After Brunner.)
Fig. 131.—Pseudoglomeris fornicata, ♀. Burma. Tribe Perisphaeriides. (After Brunner.)