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North Temperate zone. It must be remembered, however, that in view of the immense geological antiquity of the existing families of Beetles, dating back certainly to the Secondary and probably to the Palæozoic epoch, “comparatively recent” may still be of considerable antiquity.
It is somewhat singular that North and South America have no genera exclusively in common. The connection between South America and Africa seems to be shown,-by the genus Psiloptera, the mass of the species being divided between these regions, with a few widely scattered over the globe; and the American genus Actenodes, which has one species in West Africa. Somewhat allied, is the extensive genus Polybothris, strictly confined to Madagascar. The genus Agrilus is perhaps cosmopolitan, although no species of the family is recorded from New Zealand. Among the peculiarities of distribution we may notice,—the genus Sponsor, with 8 species in the island of Mauritius, 1 in Celebes, and 1 in New Guinea ; Ptosima, scattered between the United States, Mendoza in South Temperate America, South Europe, the Philippine Islands, and North China ; Polycesta, which besides inhabiting South America, North America, and Europe, has a single species in Madagascar; and Belionota, which has 8 species African, 8 Indo-Malayan, 2 Austro-Malayan, and 1 in California. The extensive genus Acmãodera, is most abundant in the warm and dry portions of the Palæarctic, Ethiopian, and Nearctic regions, with some in the Andes and South Temperate America, a few in Brazil and the West Indies, and 1 said to be from the Philippines. About one-third of the genera (containing more than half the species) have a tolerably extensive range, while the genera confined to single regions contain only about one-fourth of the total number of species.
It will, I think, be admitted, after a careful study of the preceding facts, that the regions and sub-regions here adopted, serve to exhibit, with great clearness, the chief phenomena of distribution presented by this interesting family.
LONGICORNIA. (1,488 Genera, 7,576 Species). The elegant and admired group of the 'Longicorn Beetles, is treated by continental authors as a single family, consisting of three sub-divisions—the Prionidæ, Cerambycidæ, and Lamiidæ of English entomologists. These are so closely related, and are so similar in form, habits, and general distribution, that it will be best to consider the whole as one group, noticing whatever peculiarities occur in the separate divisions. The endless structural differences among these insects, have led to their being classed in an unusual number of genera, which average little more than 5 species each; a number far below that in any of the other families we have been considering, and probably below that which obtains in any of the more extensive groups of animals or plants. This excessive subdivision of the genera, a large number of which consist of only one or two species, renders it difficult to determine with precision the relations of the several regions, since the affinities of these genera for each other are in many cases undetermined. A group of such enormous extent as this, can only be properly understood after years of laborious study; we must therefore content ourselves with such results as may be obtained from a general survey of the group, and from a comparison of the range of the several genera, by means of a careful tabulation of the mass of details given in the recent Catalogue of Messrs. Gemminger and Harold and the noble work of Lacordaire.
The proportionate extent of the three families of Longicorns is very unequal; the Prionidæ comprising about 7 per cent., the Cerambycidæ 44 per cent., and the Lamiidæ 49 per cent. of the total number of species; and the genera are nearly in the same proportions, being almost exactly 10, 40, and 50 per cent of the whole, respectively; or, 135 Prionidæ, 609 Cerambycidæ, and 746 Lamiidæ. The several regions, however, present marked differences in their proportions of these families. In the two North Temperate regions, the Cerambycidæ are considerably more numerous than the Lamiidæ, in the proportion of about 12 to 9; and in this respect the Neotropical region agrees with them, though the superiority in the proportion of Cerambycidæ is somewhat less. In the Old World tropical regions, however, and in Australia, the Lamiidæ greatly preponderate—being nearly double in the Oriental and Ethiopian regions (or as 11 to 6), while in the Australian it is as '6 to 5. The Prionidæ show a similar difference, though in a less degree; being proportionately more numerous in the North Temperate and Neotropical regions. Now, as regards the North Temperate regions, this difference can be, to some extent explained, by a difference in the habits of the insects. The Lamiidæ, which both in the larva and perfect state have exceedingly powerful jaws, exclusively frequent timber trees, and almost always such as are dead; while the Cerambycidæ, are generally more delicate and have weaker mandibles, and many of the species live on shrubs, dead twigs, foliage, and even on flowers. The immense superiority of the Tropics in the number and variety of their timber trees, and the extent of their forests, sufficiently accounts for their superiority to the Temperate regions in the development of Lamiidæ; but the great excess of Cerambycidæ in South America as compared with the rest of the Tropics, is not to be so readily explained.
Bearing in mind the different proportions of the families, as above noted, we may now consider the distribution of the Longicorns as a whole. In number of generic forms, the Neotropical region, as in so many other groups, has a marked superiority. It possesses 516 genera, 489 of which (or about 1% of the whole) are peculiar to it. The Australian and Oriental regions come next, and are exactly equal, both possessing 360 genera, and having almost exactly the same proportion (in each case a little less than ) peculiar. The Ethiopian region has 262 genera, with about 5 peculiar; the Palæarctic 196, with 51 (rather more than 1) peculiar; and the Nearctic 111, with 59 (a little more than half) peculiar. The more isolated of the sub-regions are also well characterised by peculiar genera. Thus, Chili with Temperate South America possesses 37, a large proportion being Cerambycidæ; the Malagasi group 26,
with a preponderance of Lamiidæ ; and New Zealand 12, of which the Cerambycidæ are only slightly in excess.
The relations between the Longicorn fauna of the several regions, are such as are in accordance with the dependence of the group on a warm climate and abundant vegetation; and indicate the efficiency of deserts and oceans as barriers to their migration. The Neotropical and Australian regions have only 4 genera in common, but these are sufficient to show, that there must probably once have been some means of communication between the two regions, better adapted to these insects than any they now possess. The Nearctic and Neotropical regions have 5, and the Nearctic and Palæarctic 13 genera in common and peculiar to them, the latter fact being the most remarkable, because no means of inter-communication now exists, except in high latitudes where the species of the Longicorns are very few. The Oriental and Australian regions, on the other hand, are closely connected, by having no less than 52 genera of Longicorns in common and peculiar to them. Most of these are specially characteristic of the Malay Archipelago, often extending over all the islands from Sumatra to New Guinea. This large number of wide-spread genera of course gives a character of uniformity to the entire area over which they extend; and, with analogous facts occurring in other families, has led many entomologists to reject that division of the Archipelago between the Australian and Oriental regions, which has been so overwhelmingly demonstrated to be the natural one in the case of the higher animals. The general considerations already advanced in Chapter II. enable us, however, to explain such anomalies as this, by the great facilities that exist for the transfer from island to island of such small animals, so closely connected with woody vegetation in every stage of their existence. That this is the true and sufficient explanation, is rendered clear by certain additional facts, which those who object to the sharp division of the IndoMalay and Austro-Malay sub-regions have overlooked.
An analysis of all the Malay Longicorns proves, that besides the 52 genera characteristic of the Archipelago as a whole, there are 100 genera which are confined to one or other of its component
sub-regions. Many of these, it is true, consist of single species confined to a single island, and we will not lay any stress on these; but there are also several important groups, which extend over the Indo-Malay or the Austro-Malay islands only, stopping abruptly at the dividing-line between them. For example, on the Indo-Malay side we have Euryarthrum, Leprodera, Aristobia, Coelosterna, and Entelopes, and what is perhaps even more satisfactory, the large genera A gelasta and Astathes, abundant in all the Indo-Malay islands, but having only one or two species just passing the boundary into Celebes. On the other side we have Tethionea, Sphingnotus, Arrhenotus, Tmesisternus (the last three genera abounding from New Guinea to Celebes, but totally unknown further west), Hestima, Trigonoptera, Amblymora, Stesilea, Enes, and the large genus Micracdutha, with but a single species beyond the boundary,-30 Austro-Malayan genera in all, each found in more than one island, but none of them extending west of Celebes. Here we have clear proof that the boundary line between the two great regions exists for Longicorns, as well as for all other animals; but in this case an unusually large number have been able to get across it. This, however, does not abolish the barrier, but only proves that it is not absolutely effectual in all cases. Those who maintain that the Malay Archipelago forms a single Coleopterous region, must disprove or explain the instances of limited range here adduced.
Out of nearly 1500 known genera of these insects, only one genus, Clytus, appears to be cosmopolitan. Saperda and Callichroma are the only others that perhaps occur in every region; but these are both wanting over wide tracts of the earth's surface, Saperda being absent from Tropical Africa and the Malay Archipelago; and Callichroma from the Australian region, except one species in Polynesia. Many of the genera of Longicorns have a somewhat wide and scattered distribution, indicative of decadence or great antiquity. Mallodon and Parandra are mostly. South American, but have species in Australia and Africa ; Oeme is 'found in Brazil and the United States, with one species in West
Africa; Ceratophorus has 2 species in West Africa and 1 in New Zealand. Xystrocera is mostly African, but has single species in