Page:Twentieth Century Impressions of Hongkong, Shanghai, and other Treaty Ports of China.djvu/148

 Taking the 130 really native Hongkong butterflies, and reducing the Danainæ to the genera Danais and Euplœa (both these genera are usually sub-divided into numerous sub-genera), they are distributed as follows:— The species of Cyaniris was not observed before 1906, but was then fairly numerous in Hongkong Island, and will probably establish itself there.

Of the sixteen rare species, three belong to Danais and two to Euplœa, one each to Lethe, Melanitis, Cirrochroa, Cyrestis, Rhinopalpa, Hypolimnas, Curctis, Prioneris, Pieris, and two to Caprona.

There is a very well-marked wet and dry form in the case of many Hongkong butterflies (especially in the Satyrinæ, Precis, and Lycænidæ) and four cases of insects with dimorphic females—Cethosia biblis, having the commoner form of female like the male, chiefly of a brilliant orange-red on the upper side, relieved with black; whilst the second form of female is dark grey with black, brown, and white markings; the under side agrees in both forms in colour and markings. The other examples are Hypolimnos misippus, which is rare or sporadic; Papilio memnon, with its tailed and tailless females; and P. clytia; but in this latter case the dimorphism includes both sexes. Some of the butterflies, especially amongst the Euplœa and Satyrinæ, exhibit striking and numerous varieties—some of them doubtless incipient species, though, after all, even a species is but a very stable variety, and transitory like everything else. The swarms of Danais and Euplœa are curious here. These insects collect together in hundreds about the middle of the dry season (November–December) and cling on trees and bushes in sheltered localities, packed so closely that they hide much of the foliage, and darken the air in rising when disturbed. There are many interesting biological items in the history of Hongkong butterflies, but we have only space to mention a few:—Euthalia lubcutina lays a hemispherical egg, the peculiarity of which is the numerous glandular hairs on the upper surface, each hair with a little globule of brownish, viscous fluid at the tip; these are quite visible without a lens. The larva of Gerydus chinensis is of interest as feeding entirely on aphides; that of Spindasis lohita is one of the numerous instances of Lycænid larvæ being assiduously attended by ants, for the purpose of sipping the fluid exuded by the dorsal glands of the larva. Apparently the latter, in this case, is absolutely dependent for existence on the care and attention of the ants, and is usually to be found in their nests. These ants are a species of Cremastogaster. But there are some kinds of ants here which are inimical to the mature butterfly. These lie in wait amongst flowers and seize the butterfly by the proboscis as it feeds. A small pale yellow or while spider, with its legs tightly appressed to its body, likewise ambushes in flowers. In spite of its small size—about ¼-inch in diameter—it not only seizes, but sometimes manages to hold and kill, a large Papilio. This spider is almost indistinguishable amongst white or yellow blossoms. Besides the operations of the native woodcutters, which destroy many eggs and larvæ and tend to eradicate food plants, the increase of butterflies in South China is chiefly and to an enormous extent checked (especially amongst the Hesperiidæ) by egg and larva parasites, chiefly Hymenopterous, which are extremely numerous in South China. In the case of a moth, Metanestria punctata, whose larva feeds on fir-trees, and in certain years often defoliates large areas in China, examination of a great number of pupæ showed that fully 75 per cent. had been destroyed, chiefly by Dipterous and Hymenopterous parasites, whilst the eggs of the moth were heavily parasitised by Hymenoptera. No doubt these parasites always appear whenever the moth becomes very abundant. The insectivorous birds here destroy few mature butterflies, though they account for numbers of eggs, larvæ, and pupæ. I am, however, of opinion that on the whole the butterfly, having passed through manifold dangers in its immature stages, has few enemies in its adult state.

The geographical distribution of animals changes slowly in the natural course of things, but modern civilisation and constant and rapid communication with all parts of the world tends to effect some of these changes more rapidly, and, we may expect, will eventually cause many more species to become extinct and some almost cosmopolitan. Hongkong, as a focus for a continuous stream of traffic from near and distant countries, and, possessing a sub-tropical climate to which many animals and plants can adapt themselves, seems exceptionally well situated for observation of some of these phenomena, for exotic insects may be expected to occur frequently, and some of them to find a suitable habitat in the island. For many new plants have certainly been introduced or found their way lo Hongkong within the last fifty years, and some of them now flourish here; and butterflies, like man and most terrestrial animals are, directly or indirectly, dependent for existence on the vegetable kingdom. The small area of the island lends itself specially to the observation of the increase and decrease of native species, and the arrival of immigrants.

In conclusion, Hongkong possesses a very bright, varied, and individually numerous butterfly fauna, which enhances the beauty and life of the island even more than the birds which, with a few exceptions, are not particularly striking in plumage. At Foochow, about midway between Hongkong and Shanghai, the vegetation changes, and is, says Mr. S. T. Dunn, superintendent of the Afforestation Department at Hongkong, an almost equal intermingling of tropical and temperate forms. At Shanghai, about 900 miles north of Hongkong, so far as the vegetation is concerned, one might imagine oneself in England, and some of the commonest butterflies there are species of Colias and Goneptcryx, the familiar "Clouded Yellows" and "Brimstones"—typically Palæarctic genera.