in Porto Santo the brightly coloured ones preponderate, and in fact are all but universal. Both extremes do nevertheless occur in both islands, the tendency being merely, in either case, to assume the particular modification characteristic of the spot[58]". And so it is with the outline and sculpture (no less than with bulk and hue): they also are equally liable to disturbance from physical causes, as indeed has been already insisted upon. Like most of the minutiae of variation, however, to which we have called attention, it is more particularly on islands that this is to be observed,--isolation, during an interval sufficiently long, appearing to possess some especial control over the external contour and surface of the insect races. Thus, in the Madeiras, for instance, the _Caulotropis lucifugus_ has its prothorax more distinctly punctured, and its elytra more perceptibly striated, in the principal island, than on any of the smaller members of the group; in Porto Santo, indeed, it is almost free from sculpture of any kind; whilst its ally, the _C. conicollis_, apart from being somewhat larger, is, on the contrary, both more punctured and striated on the Dezerta Grande than it is in Madeira proper. The _Omias Waterhousei_, again (in addition to its slightly increased bulk and less shining envelope, in that locality), is more lightly impressed on the Dezerta than it is in Madeira and, not to mention other differences, the _Ellipsodes glabratus_ is densely beset with most minute granules on that same rock--whereas on the mountain slopes of the central mass, it is highly polished and glabrous. The _Helops confertus_, we have intimated at a previous page, is less coarsely sculptured in the lofty regions of Madeira, than in the lower ones: and the _H. futilis_ has its elytral tubercles apparent in Madeira proper, but evanescent on the Dezerta Grande. The _Eurygnathus Latreillei_ assumes a permanent variety on the Dezerta, the insect having become modified through a long isolation on those weather-beaten heights,--here it not only attains a more gigantic stature than in Porto Santo, but is invariably also more parallel and opake, has the sides of its prothorax more recurved, with the punctures towards the lateral angles almost obsolete, and the striae of its elytra somewhat more evidently punctate[59]. Such examples, however, might be multiplied _ad infinitum_; and I will not therefore devote further space to the bringing together of facts which it is hardly possible will be disputed,--especially as it has been my wish, in the present chapter, merely to _enumerate_ what the organs and characters principally are which are more peculiarly sensitive to change, throughout the Annulose tribes. This I may venture to hope, though briefly, I have in part done; and I will consequently pass on to other considerations, which, even if somewhat alien to the immediate question of insect instability, should scarcely be altogether omitted in a treatise like this.