« EelmineJätka »
CETONIIDAE (120 Genera, 970 Species)
As representative of the enormous group of the Lamellicorns, which, according to continental entomologists, forms a single family numbering nearly 7,000 species, we take the Cetoniidae or Rose-Chafers. These comprise a number of the most brilliant and beautifully-coloured insects, including the gigantic Goliathi, which are among the largest of known beetles. They have been assiduously collected in every part of the world, and their classification has been elaborated by many of our most eminent entomologists. The Cetoniidae are especially abundant in tropical and warm countries, yet far more so in the Old World than in the New ; and in the Old World, the Ethiopian region exhibits a marvellous richness in this family, no less than 76 genera being found there, while 64, or more than half the total number, are peculiar to it. Next in richness, though still very far behind, comes the Oriental region, with 29 genera, 17 of which are peculiar. The Neotropical has only 14 genera, but all except two are peculiar to it, and one of these is not found out of the New World. The Australian region has 11 genera, three only being peculiar. The Palaearctic region has 13, with 4 peculiar; the Nearctic 7, with 2 peculiar. The affinities of the regions for each other, as indicated by the genera confined to two adjacent regions, are in this family somewhat peculiar. The Ethiopian and Oriental show the most resemblance, 6 genera being common and peculiar to the two; the Oriental and the Australian are unusually well contrasted, having only one genus exclusively in common, while 8 genera are found in the Indo-Malay Islands which do not cross the boundary to the Austro-Malayan division, and several others only pass to the nearest adjacent islands; on the other hand, the only large Australian genus, Schizorhina, is found in many parts of the Moluccas, but not further west. The Australian and Neotropical regions exhibit no direct affinity, the nearest ally to the South American Gymnetidae being Clinteria, an African and Asiatic genus; while not a single genus is common to Australia and South America. The Nearctic and Palaearctic regions have 3 genera in common, which are found in no other part of the world.
Among the special features of interest connected with the distribution of this family, we must first notice the exceptional richness of Madagascar, which alone possesses 21 peculiar genera. South Africa is also very rich, having 8 peculiar genera. Stethodesma is very peculiar, being divided between South America and Mexico on the one hand, and West and South Africa on the other. Stalagmosoma is a desert genus, ranging from Persia to Dongola. No genus is cosmopolitan, or even makes any approach to being so, except Valgus, which occurs in all the regions except the Neotropical; and even the family seems to be not universally distributed, since no species are recorded either from New Zealand, the Pacific Islands, or the Antilles.
The facts here brought forward, lead us to the conclusion that the Cetoniidae are an Old-World tropical family, which had been well developed in Africa and Asia before it spread to Australia and America; and that it is only capable of being freely dispersed in the warmer regions of the earth. This view will explain the absence of affinity between the Australian and Neotropical regions, the only closer connection between which, has almost certainly occurred in the colder portions of the Temperate Zone.
BUPRESTIDAE. (109 Genera, 2,686 Species.)
The next family suited to our purpose is that of the Buprestidae, consisting as it does of many large and some gigantic species, generally adorned with brilliant metallic colours, and attracting attention in all warm countries. Although these insects attain their full development of size and beauty only in the Tropics, they are not much less abundant in the warmer parts of the Temperate zone. In the Catalogue of the Coleoptera of Europe and the Mediterranean Basin, by M. de Marseul (1863), we find 317 species of Buprestidae enumerated, although the district in question only forms a part of the Palaearctic region, which would thus seem to possess its full proportion of the species of this family. Confining ourselves to the generic forms, we find far less difference than usual between the numbers possessed by the tropical and the temperate regions; the richest being the Australian, with 47 genera, 20 of which are peculiar; and the poorest the Nearctic, with 24 genera, of which 7 are peculiar. The Oriental has 41 genera, 14 of which are peculiar; the Neotropical 39, of which the large proportion of 18 are peculiar; the Ethiopian 27, of which 6 are peculiar; and the Palaearctic also 27, but with 9 peculiar. A most interesting feature in the distribution of this family, is the strong affinity shown to exist between the Australian and Neotropical regions, which have 4 genera common to both and found nowhere else ; but besides this, the extensive and highly characteristic Australian genus, Stigmodera, is closely related to a number of peculiar South American genera, such as Conognatha, Hyperantha, Dactylozodes, the last altogether confined to Chili and Temperate South America. Here we have a striking contrast to the Cetoniidae, and we can hardly help concluding, that, as the latter is typically a tropical group, so the present family, although now so largely tropical, had an early and perhaps original development in the temperate regions of Australia, spreading thence to Temperate South America as well as to the tropical regions of Asia and Africa. The Australian and Oriental regions have 4 genera exclusively in common, but they also each possess a number of peculiar or characteristic genera, such as the Indo-Malayan Catocantha (which has only a single species in the Moluccas) and nine others of less importance; and the exclusively Austro-Malayan genus, Sambus, with five smaller groups, and Cyphogastra, with only 2 Indo-Malay species. The Oriental and Ethiopian regions are very distinct, only possessing the single genus, Sternocera, exclusively in common. The Nearctic and Palaearctic are also distinct, only one genus, Dicerca, being confined to America (North and South) and Europe, a fact which again points to a southern origin for this family, and its comparatively recent extension into the 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 Palaeozoic 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 Polyboth ris, 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; Płosima, 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 Acmaeodera, is most abundant in the warm and dry portions of the Palaearctic, 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 Prionidae, Cerambycidae, and Lamiidae 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 Prionidae comprising about 7 per cent, the Cerambycidae 44 per cent., and the Lamiidae 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 Prionidae, 609 Cerambycidae, and 746 Lamiidae. The several regions, however, present marked differences in their proportions of these families. In the two North Temperate regions, the Cerambycidae are considerably more numerous than the Lamiidae, in the proportion of about 12 to