_Anchomenus aptinoides_ Allied to a species from the Canaries. _Bembidium hesperus_ Allied to the European _B. laetum_. DYTISCIDAE. _Agabus godmanni_ Allied to the European _A. dispar_. COLYDIIDAE. _Tarphius wollastoni_ A genus almost peculiar to the Atlantic islands. {254} ELATERIDAE. _Heteroderes azoricus_ Allied to a Brazilian species. _Elastrus dolosus_ Belongs to a peculiar Madagascar genus! MELYRIDAE. _Attalus miniaticollis_ Allied to a Canarian species. RHYNCOPHORA. _Phlaeophagus variabilis_ Allied to European and Atlantic species. _Acalles droueti_ A Mediterranean and Atlantic genus. _Laparocerus azoricus_ Allied to Madeiran species. _Asynonychun godmansi_ A peculiar genus, allied to _Brachyderes_, of the south of Europe. _Neocnemis occidentalis_ A peculiar genus, allied to the European genus _Strophosomus_. HETEROMERA. _Helops azoricus_ Allied to _H. vulcanus_ of Madeira. STAPHYLINIDAE. _Xenomma melanocephala_ Allied to _X. filiforme_ from the Canaries. This greater amount of speciality in the beetles than in the birds may be due to two causes. In the first place many of these small insects have no doubt survived the glacial epoch, and may, in that case, represent very ancient forms which have become extinct in their native country; and in the second place, insects have many more chances of reaching remote islands than birds, for not only may they be carried by gales of wind, but sometimes, in the egg or larva state or even as perfect insects, they may be drifted safely for weeks over the ocean, buried in the light stems of plants or in the solid wood of trees in which many of them undergo their transformations. Thus we may explain the presence of three common South American species (two elaters and a longicorn), all wood-eaters, and therefore liable to be occasionally brought in floating timber by the Gulf Stream. But insects are also immensely more numerous in species than are land-birds, and their transmission would be in most cases quite involuntary, and not dependent on their own powers of flight as with birds; and thus the chances against the same species being frequently carried to the same island would be considerable. If we add to this the dependence of so {255} many insects on local conditions of climate and vegetation, and their liability to be destroyed by insectivorous birds, we shall see that, although there may be a greater probability of insects as a whole reaching the islands, the chance against any particular species arriving there, or against the same species arriving frequently, is much greater than in the case of birds. The result is, that (as compared with Britain for example) the birds are, proportionately, much more numerous than the beetles, while