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Show 1878.] HEMIPTERA OF ST. HELENA. 459 Here I may be permitted to quote a remark by Mr. Darwin on this pointl:-"In Africa, several forms characteristic of Europe and some few representatives of the flora of the Cape of Good Hope occur on the mountains of Abyssinia. At the Cape of Good Hope a very few European species, believed not to have been introduced by man, and on the mountains several representative European forms are found which have not been discovered in the intertropical parts of Africa. Dr. Hooker has also lately shown that several of the plants living on the upper parts of the lofty island of Fernando Po and on the neighbouring Cameroon Mountains, in the Gulf of Guinea, are closely related to those on the mountains of Abyssinia, and likewise to those of Temperate Europe. It now also appears, as I hear from Dr. Hooker, that some of these same temperate plants have been discovered by the Rev. R. T. Lowe on the mountains of the Cape-Verde Islands. This extension of the same temperate forms, almost under the equator, across the whole continent of Africa and to the mountains of the Cape-Verde archipelago, is one of the most astonishing facts ever recorded in the distribution of plants "2. Mr. Darwin then proceeds to show how in a glacial epoch the temperate flora might have invaded the whole of Africa, and at the return of warmer conditions been driven up the mountains, or in some cases become gradually acclimatized. In connexion with this possible, and, as it seems to me, probable, community of origin of the floras of the Cape (in part) and of St. Helena, the significance of the occurrence at the former place of several Coleoptera and Hemiptera closely allied to, if not identical with, St.-Helenian species, is not to be overlooked3. It is not to be wondered at, then, that we do not find, in the parts of Africa nearest St. Helena, much, if any, relationship to the island fauna and flora. That such relationship, so far as community of origin is concerned, once existed, I have little doubt ; but the return to tropical conditions and the reestablishment of the tropical fauna and flora have obliterated, except on the mountain-summits, all traces. And St. Helena by its isolated position and temperate climate (the mean temperature of the year being only about 61°) is to all purposes a mountain. The affinity of the Hemipterous genus Megarhaphis to the African Macrorhaphis (of which one species is from the Cape, and the other.-rather doubtful as to the genus-is from the Congo) seems to be an exception; but as we do not know the exact nature of the locality whence the Congo species was derived, and as it is as likely as not to be a mountain and not a tropical insect, it may after all prove our case by being a descendant of one and the same Palaearctic ancestor as the Cape and St.-Helenian species. There still remain some elements in the fauna and flora of St. Helena to be accounted for. 1 Origin of Species, p. 337. 2 See also Professor Oliver's ' Flora of Tropical Africa,' in which the occurrence of several species, not only European but even Arctic, is recorded. 3 Certain European Hemiptera are also natives of the Cape. 30* |
