In like manner, the genus _Tarphius_ is distinctively Madeiran. I have detected nearly twenty well-defined species of it in that group; yet, out of so large a number, two only have occurred beyond the central island. Now the _Tarphii_ are, also, wingless; and creatures of very sluggish propensities,--scarcely ever stirring from the masses of loose rotting timber which they so assimilate in hue, and to the under sides of which they affix themselves, day and night. Although difficult to investigate in their precise economy, it is extremely probable (may I not say, certain?) that some important and peculiar office is assigned to them in the remote upland districts to which they exclusively belong: and there cannot be any question, to a person who has studied them carefully on the spot, but that the region which they now inhabit is the actual area of their primaeval appearance on this earth. Many kindred species may of course have been lost, during those gigantic subsidences which caused the Madeiras to be shaped out, and to tell their tale above the waves as ruins of an ancient land; yet our existing cluster of forms could not have wandered far at that early period, from the Serras and ridges of their birth,--perhaps not _so_ far indeed (considering the limited bounds within which they are now confined, and that time should in reality have increased their range rather than diminished it) as they have succeeded in doing at the present day. Hence we may reasonably conclude, that Madeira proper is an example of what we have alluded to in a preceding page,--namely, of the accidental retention, during a vast downward movement, of a nucleus of small specific areas of colonization, the colonizers of which _had not extended elsewhere_. But I stated, that two of the above-mentioned _Tarphii_ have occurred beyond the central mass. It is in Porto Santo that they make their appearance; nevertheless, since one of them is apparently peculiar to that island, it is only the _T. Lowei_, Woll. (an insect of a different, and more active, nature than the rest) which has violated that _local exclusiveness_ which would seem to be almost a generic character, as it were, of its allies. That species, however, both in its manners and aspect, recedes materially from the remainder. Although, like them, nocturnal in its habits, it is able to run with considerable velocity; and, instead of attaching itself to the blocks of putrefying wood, which both fall and decay _in situ_ on those elevated tracts, it hides within the bunches of _Evernia scopulorum_ and _prunastri_ which clothe the trunks of living trees, and fill up the crevices of the weather-beaten peaks. Hence, when contrasted with its comrades, we can easily understand how the varied processes of accidental transportation would operate to increase the range of a creature which differs so essentially, in many respects, from them. It is indeed, not unfrequently, brought down, at