Insects.—Owing to the researches of the Rev. T. Blackburn we have now a fair knowledge of the Coleopterous fauna of these islands. Unfortunately some of the most productive islands in plants—Kaui and Maui—were very little explored, but during a residence of six years the equally rich Oahu was well worked, and the general character of the beetle fauna must therefore be considered to be pretty accurately determined. Out of 428 species collected, many being obviously recent introductions, no
less than 352 species and 99 of the genera appear to be quite peculiar to the archipelago. Sixty of these species are Carabidæ, forty-two are Staphylinidæ, forty are Nitidulidæ, twenty are Ptinidæ, twenty are Ciodidæ, thirty are Aglycyderidæ, forty-five are Curculionidæ, and fourteen are Cerambycidæ, the remainder being distributed among twenty-two other families. Many important families, such as Cicindelidæ, Scarabœidæ, Buprestidæ, and the whole of the enormous series of the Phytophaga are either entirely absent or are only represented by a few introduced species. In the eight families enumerated above most of the species belong to peculiar genera which usually contain numerous distinct species; and we may therefore consider these to represent the descendants of the most ancient immigrants into the islands.
Two important characteristics of the Coleopterous fauna are, the small size of the species, and the great scarcity of individuals. Dr. Sharp, who has described many of them,[[126]] says they are "mostly small or very minute insects," and that "there are few—probably it would be correct to say absolutely none—that would strike an ordinary observer as being beautiful." Mr. Blackburn says that it was not an uncommon thing for him to pass a morning on the mountains and to return home with perhaps two or three specimens, having seen literally nothing else except the few species that are generally abundant. He states that he "has frequently spent an hour sweeping flower-covered herbage, or beating branches of trees over an inverted white umbrella without seeing the sign of a beetle of any kind." To those who have collected in any tropical or even temperate country on or near a continent, this poverty of insect life must seem almost incredible; and it affords us a striking proof of how erroneous are those now almost obsolete views which imputed the abundance, variety, size, and colour of insects to the warmth and sunlight and luxuriant vegetation of the tropics. The facts become quite intelligible, however, if we consider that only
minute insects of certain groups could ever reach the islands by natural means, and that these, already highly specialised for certain defined modes of life, could only develop slowly into slightly modified forms of the original types. Some of the groups, however, are considered by Dr. Sharp to be very ancient generalised forms, especially the peculiar family Aglycyderidæ, which he looks upon as being "absolutely the most primitive of all the known forms of Coleoptera, it being a synthetic form linking the isolated Rhynchophagous series of families with the Clavicorn series. About thirty species are known in the Hawaiian Islands, and they exhibit much difference inter se." A few remarks on each of the more important of the families will serve to indicate their probable mode and period of introduction into the islands.
The Carabidæ consist chiefly of seven peculiar genera of Anchomenini comprising fifty-one species, and several endemic species of Bembidiinæ. They are highly peculiar and are all of small size, and may have originally reached the islands in the crevices of the drift wood from N.W. America which is still thrown on their shores, or, more rarely, by means of a similar drift from the N.-Western islands of the Pacific.[[127]] It is interesting to note that peculiar species of the same groups of Carabidæ are found in the Azores, Canaries, and St. Helena, indicating that they possess some special facilities for transmission across wide oceans and for establishing themselves upon oceanic islands. The Staphylinidæ present many peculiar species of known genera. Being still more minute and usually more ubiquitous than the Carabidæ, there is no difficulty in accounting for their presence in the islands by the same means of dispersal. The Nitidulidæ, Ptinidæ, and Ciodidæ being very small and of varied habits, either the perfect insects, their eggs or larvæ, may have been introduced either by water or wind carriage, or through the agency of birds. The Curculionidæ, being wood bark or nut borers, would have considerable facilities for transmission by floating timber, fruits, or nuts; and the eggs or larvæ of the
peculiar Cerambycidæ must have been introduced by the same means. The absence of so many important and cosmopolitan groups whose size or constitution render them incapable of being thus transmitted over the sea, as well as of many which seem equally well adapted as those which are found in the islands, indicate how rare have been the conditions for successful immigration; and this is still further emphasized by the extreme specialisation of the fauna, indicating that there has been no repeated immigration of the same species which would tend, as in the case of Bermuda, to preserve the originally introduced forms unchanged by the effects of repeated intercrossing.
Vegetation of the Sandwich Islands.—The flora of these islands is in many respects so peculiar and remarkable, and so well supplements the information derived from its interesting but scanty fauna, that a brief account of its more striking features will not be out of place; and we fortunately have a pretty full knowledge of it, owing to the researches of the German botanist Dr. W. Hildebrand.[[128]]
Considering their extreme isolation, their uniform volcanic soil, and the large proportion of the chief island which consists of barren lava-fields, the flora of the Sandwich Islands is extremely rich, consisting, so far as at present known, of 844 species of flowering plants and 155 ferns. This is considerably richer than the Azores (439 Phanerogams and 39 ferns), which though less extensive are perhaps better known, or than the Galapagos (332 Phanerogams), which are more strictly comparable, being equally volcanic, while their somewhat smaller area may perhaps be compensated by their proximity to the American continent. Even New Zealand with more than twenty times the area of the Sandwich group, whose soil and climate are much more varied and whose botany has been thoroughly explored, has not a very much larger number of flowering plants (935 species), while in ferns it is barely equal.
The following list gives the number of indigenous species in each natural order.