THE ENVIRONMENT
There are more than 200 recorded species and forms of butterflies. One of them, the birdwing butterfly (Troides helena) is endangered and protected by the Wild Animals Protection Ordinance and the Animals and Plants (Protection of Endangered Species) Ordinance. Among the many local moths are the giant silkworm moths, including the cynthia, fawn, atlas and moon. The atlas has an average wing span of 23 centimetres and the moon, 18 centimetres.
Two local plant bugs are especially noted for their colour and shape. They are the rare, spotted tea bug, which has been recorded only on hilltops; and the lantern fly, which has delicately coloured wings and a remarkably long forehead. Dragonflies and damselflies are common, as are wasps and metallic-coloured beetles. Of particular interest is the giant red- spotted longhorn beetle which feeds on mountain tallow and wood-oil trees. Many other species of longhorn beetles infest living or weakened trees.
Since its introduction to Hong Kong in 1938, the African giant snail has become a major pest in vegetable crops and gardens. Farmers are also troubled by several types of slugs. One of these, veronicella, is large and black and sufficiently different from the other slugs to be placed in a separate family.
Aquatic Fauna
Despite its sub-tropical position, Hong Kong straddles two large zoogeographical regions: the Palaeo-Arctic temperate region to the north and the Indo-Pacific tropical region to the south. This creates a tremendous diversity of fish, crustacea and molluscs, of which at least 150 species are fished for food in surrounding seas.
A largely tropical resident marine fauna is bolstered when the monsoonal flow brings in cooler waters, with transient species like the yellow croaker and melon seed, typically found off Northern China and Japan.
Local waters range broadly from the predominantly brackish in the west to the less turbid and more oceanic in the east. Seasonal rainfall affecting the outflow of the Pearl River, the largest river in southern China, results in the intrusion of brackish waters into areas which for much of the year experience clear oceanic waters. Animals favouring brackish waters include the Chinese white dolphin, one of 12 species of cetaceans that make up the only aquatic mammals found in the territory. Typical of the more oceanic is the red pargo, one of a number of sea breams whose fry are abundant along the shores of Mirs Bay and are captured in the early spring months to provide a mainstay for mariculture.
The natural history of many common shore animals, particularly the more sedentary molluscs and crustacea of rocky shores and mangroves has been studied, but broad gaps remain in the knowledge of local marine fauna. An expansion of marine recreation, including boating, sport fishing and scuba diving, coupled with an increased concern for the visible effects of pollution and dredging and dumping in local waters has focused attention on this only in recent years. Even the less common commercial fish and the corals that reach the northernmost extent of their range in Hong Kong remain poorly documented, not to mention the myriad less familiar worms, urchins, starfish, pens and the more microscopic planktonic forms.
The habitats of Hong Kong's coastal areas have experienced changes in the last decade paralleling the more visible changes above high water. Inevitable detrimental changes in the fauna are largely unrecorded, but those which have been identified are being countered
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