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Show 1878.] HEMIPTERA OF ST. HELENA. 457 identical with another, Cape-of-Good-Hope species-the significance of which latter facts will be alluded to in connexion with the flora. Again, the genus Euxestus was known from Madeira only, till M r. Wollaston discovered another species in St. Helena. But as the most remarkable fact in the coleopterous fauna of St. Helena is the enormous preponderance of Cossonidee-more than a quarter of the endemic species belonging to that family-which seem to find there their metropolis, we ought, if the line of migration is by Madeira & c , to find in the latter a significant development of this family. And so we do. " In the Madeiran and Canarian groups," writes Mr. Wollaston1, "there is scarcely any fact [the insular-loving nature of the Cossonidee] more distinctly observable- where every detached rock is tenanted by some one representative, or more, of this particular department. Nor are trees and shrubs (which seldom flourish in localities thus weather-beaten and exposed) by any means essential for their support, the pithy stems of the ordinary plants being amply sufficient to sustain them ; and I have frequently found the stalks of dead thistles and Umbelliferae to be perforated through and through by their ravages." Mr. Wollaston found 19 species in Madeira and 14 in the Canaries. The Anthri-biidce (which include the next largest number of endemic species in St. Helena) indicate a like derivation ; but enough has, I think, been brought forward to show both the Palaearctic origin and probable route of migration of the Coleoptera of St. Helena. The Hemiptera are not fitted (from the reasons already given) to teach us so much as the Coleoptera ; but 12 at least, if not all, of the 13 non-peculiar genera are Palaearctic, and many of them Madeiran. The peculiar genera have also nearly all strong affinities with Palaearctic genera. Just as the whole facies of the Madeiran Hemiptera is European, so that of the St.-Helenian is Madeiran and European. The characteristics of the Arachnida and of the terrestrial Mollusca have already been pointed out. But let us now see if there be any thing in the manner of life of the aboriginal animals of St. Helena which would make their passage across the sea not only a possible but a probable occurrence. If we can find that a majority of them are connected with plants, it is not difficult to imagine how they might have been drifted by sea-currents to the island ; but if, in addition, it turned out that many inhabited the interior parts of plants, their carriage across the sea would pass from the region of possibility into that of probability. Mr. Wollaston has carefully recorded the modus vivendi of the St.- Helenian Coleoptera; so we will try and prove our case from his evidence. At least half of the 12 endemic species of the genus Bembidium have the very abnormal habit, for that genus, of living within the dead and rotting stems of the tree ferns. (I m a y note here that in the Madeiran group 10, in the Canaries 14 (7 peculiar), and in the Cape-Verds 5 species of the genus have been found.) The following St.-Helenian genera are also, amongst others, especially 1 Trans. Entom. Soc. London, 1873, iv. p. 433. PROC. ZOOL. Soc-1878, No. XXX. 30 |