« EelmineJätka »
THE DISTRIBUTION OF SOME OF THE MORE IMPORTANT FAMILIES
AND GENERA OF INSECTS.
ALTHOUGH insects are, for the most part, truly terrestrial animals, and illustrate in a very striking manner the characteristic phenomena of distribution, it is impossible here to treat of them in much detail. This arises chiefly from their excessive numbers, but also from the minuteness and obscurity of many of the groups, and our imperfect knowledge of all but the European species. The number of described species of insects is uncertain, as no complete enumeration of them has ever been made; but it probably exceeds 100,000, and these may belong to somewhere about 10,000 genera—many times more than all vertebrate animals together. Of the eight Orders into which Insects are usually divided, only two-the Coleoptera and Lepidoptera -have been so thoroughly collected in all parts of the globe that they can be used, with any safety, to compare their distribution with that of vertebrate animals; and even of these it is only certain favourite groups which have been so collected. Among Lepidoptera, for example, although the extensive group of Butterflies may be said, in a general sense, to be thoroughly well known-every spot visited by civilized man having furnished its quota to our collections yet the minute Tineidæ, or even the larger but obscure Noctuidæ, have scarcely been collected at all in tropical countries, and any attempt to study their geographical distribution would certainly lead to erroneous results. The same thing occurs, though perhaps in a less degree, among the Coleoptera. While the Carabidæ, Buprestidæ, and
Longicorns of the Tropics, are almost as well known as those of the Temperate Zones, the Staphylinidæ, the smaller Elateridæ, and many other obscure and minute groups, are very imperfectly represented from extra-European countries. I therefore propose to examine with some care the distribution of the Butterflies, and the Sphingina among Lepidoptera, and the following large and well-known families of Coleoptera :-Cicindelidæ, Carabidæ, Lucanidæ, Cetoniidæ, Buprestidæ, and the three families of Longicorns. These families together contain over 30,000 species, classed in nearly 3,000 genera, and comprise a large proportion of the best known and most carefully studied groups. We may therefore consider, that a detailed examination of their distribution will lead us to results which cannot be invalidated by any number of isolated facts drawn from the less known members of the class.
Range of Insects in Time.-In considering how much weight is to be given to facts in insect distribution, and what interpretation is to be put upon the anomalies or exceptional cases that may be met with, it is important to have some idea of the antiquity of the existing groups, and of the rate at which the forms of insect life have undergone modification. The geological record, if imperfect in the case of the higher animals, is fragmentary in the extreme as regards indications of former insect life; yet the positive facts that it does disclose are of great interest, and have an important bearing on our subject. These facts and the conclusions they lead to have been discussed in our first volume (p. 166), and they must be carefully weighed in all cases of apparent conflict or incongruity between the distribution of insects and that of the higher animals.
Sub-order-LEPIDOPTERA RHOPALOCERA, or BUTTERFLIES.
FAMILY 1.-DANAIDÆ. (24 Genera, 530 Species.)
The Danaidæ are now held to comprehend, not only the whole of the group so named by Doubleday, but a large portion of the Heliconidæ of that author. Their range is thus extended over the whole of the tropical regions. A few species spread northwards into the Palæarctic and Nearctic regions, but these are only stragglers, and hardly diminish the exclusively tropical character of the group. The more remarkable genera are, -Hestia (10 sp.), and Ideopsis (6 sp.), confined to the Malayan and Moluccan districts ; Danais (50 sp.), which has the range of the whole family; Euplæa (140 sp.), confined to the Oriental and Australian regions, but especially abundant in the Malayan and Moluccan districts; Hamadryas (4 sp.), Australian region only. The remaining genera constitute the Danaioid Heliconidæ, and are strictly confined to Tropical America, except a few species which extend into the southern parts of the Nearctic region. The chief of these genera are :
Ithomia (160 sp.), Melinæa (18 sp.), Napeogenes (20 sp.), Mechanitis (4 sp.), Ceratina (32 sp.), Dircenna (10 sp.), and Lycorea (4 sp.). Florida, Louisiana, and Southern California, mark the northern extent of these insects.
FAMILY 2.--SATYRIDÆ. (60 Genera, 835 Species.)
This family has an absolutely universal distribution, extending even into the Arctic and Antarctic regions. Many of the genera are, however, restricted in their range.
Hætera, Lymanopoda, Calisto, Corades, Taygetis, Pronophila, Euptychia, and some allied forms (25 genera in all) are Neotropical, the last named extending north to Canada; Debis, Melanitis, Mycalesis and Ypthima, are mostly Oriental, but extending also into the Australian and the Ethiopian regions; Gnaphodes, Leptoneura, and a few other small genera, are exclusively Ethiopian ; Xenica, Hypocista, and Heteronympha, are Australian ; Erebia, Satyrus, Hipparchia, Canonymphu, and allies, are mostly Palæarctic, but some species are Ethiopian, and others Nearctic; Chionabas, is characteristic of the whole Arctic regions, but is also found in Chili and the Western Himalayas. The peculiar genera in each region are,— Neotropical, 25; Australian, 7; Oriental, 11; Ethiopian, 5; Palæarctic, 3; Nearctic, 0.
FAMILY 3.-ELYMNIIDÆ. (1 Genus, 28 Species.)
The genus Elymnias, which constitutes this family, is characteristic of the Malayan and Moluccan districts, with some species in Northern India and one in Ashanti. It thus agrees with several groups of Vertebrata, in showing the resemblance
of Malaya with West Africa independently of the Peninsula of India.
FAMILY 4. MORPHIDÆ. (10 Genera, 106 Species.)
The Morphidæ are a gronp of generally large-sized butterflies, especially characteristic of the Malayan and Moluccan districts, and of Tropical America ; with a few species extending to the Himalayas on the west, and to Polynesia on the east.
The genera are :
Amathusia (6 sp.), Northern India to Java; Zeuvidia (9 sp.), the Malay district; Discophora (7 sp.), Northern India to Philippines, Java and Timor; Enispe (3 sp.), Northern India; Hyades (15 sp.), Moluccan and Polynesian districts, except one species in Java; Clerome (11 sp.), Northern India to Philippines and Celebes ; Æmona (1 sp.), Sikhim ; Hyantis (1 sp.), Waigiou; Thaumantis (10 sp.), Indo-Chinese and Malayan districts ; Morpho (40 sp.), Neotropical region, Brazilian and Central American sub-regions.
FAMILY 5. BRASSOLIDÆ (7 Genera, 62 Species.)
The Brassolidæ have the same distribution as the genus Morpho. The genera are :
Brassolis (5 sp.); Opsiphanes (17 sp.); Dynastor (2 sp.); Penetes (1 sp.); Caligo (21 sp.); Narope (5 sp.); and Dasyopthalma (3 sp.)