. The Cambridge natural history. Zoology. 226 ORTHOPTERA. abbreviated, and on the whole is of subordinate importance to the other three. These latter thus form four chief areas or iields, viz.—1, mediastinal or marginal; 2, scapular or radial; 3, median; and 4, anal. These nervures and divisions may be traced in a large number of existing and fossil Blattidae, but there are forms existing at present which it is difficult to reduce to the same plan. In Euthyrhaplm, found in the Pacific Islands, the hind wings are long and project Ijeyond the tegmina, and have a very peculiar arrangement of the
. The Cambridge natural history. Zoology. 226 ORTHOPTERA. abbreviated, and on the whole is of subordinate importance to the other three. These latter thus form four chief areas or iields, viz.—1, mediastinal or marginal; 2, scapular or radial; 3, median; and 4, anal. These nervures and divisions may be traced in a large number of existing and fossil Blattidae, but there are forms existing at present which it is difficult to reduce to the same plan. In Euthyrhaplm, found in the Pacific Islands, the hind wings are long and project Ijeyond the tegmina, and have a very peculiar arrangement of the nervures ; the species of Holocam-psa, also possess abnormal alar organs, while the struc- ture of these parts in Diaj)liana (Fig. 122) is so peculiar that Brunner wisely refrains from attempting to homologise their nervures with those of the more normal Blattidae. The alar organs are frequently extremely different in the two sexes of the same species of Blattidae, and the hind wing may differ much from the teg- men as regards degree of departure from the normal So that it is not a matter for surprise that the nervures in different genera cannot be satisfactorily homologised. But the most peculiar wings in the family are the folded structures found in some forms of the groups Ectobiides and Oxyhaloides [Anaplectinae and Plectopterinae of de Saussiu-e]. These have been studied by de Saussui-e,-' and in Fig. 123 we reproduce some of his sketches, from which it will be seen that in B and 0 the wing is divided by an unusual cross-joint into two parts, the apical portion being also longitudinally divided into two pieces a and l. Such a form of wing as is here shown has no exact parallel in any of the other groups of Insects, though the earwigs and some of the Coleoptera make an approach to it. This structure permits a very perfect folding of the wing in repose. The peculiarities exhibited have been explained by de Saussiu-e somewhat as follows. In the ordinary condition of Orthopt
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