ENG-1974 — Page 279

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NATURAL HISTORY

long forehead. Other commonly found insects include many types of dragon and dam- sel flies, together with metallic coloured beetles and wasps. Weather conditions in 1974 were such that long-horn beetles were plentiful. Of particular interest is the Large Spotted Batocera Long-horn Beetle, which feeds on mountain tallow trees.

The largest of the land molluscs is the African Giant Snail, a specimen of which has been found measuring six inches in length. This species was introduced in 1938 and has become a crop and garden pest. The large black slug, Veronicella, is sufficiently different from all other slugs to be placed in a separate family.

Aquatic Life

Marine life forms in Hong Kong are diverse and mainly tropical in character, comprising a relatively large number of commercially important species of fish, crus- tacea, and molluscs. The discharge of the largest fresh water system in South China to the west, and the prevailing Taiwan current from the north-east, have created a situation where the westerly sector of Hong Kong has a predominantly brackish water fauna, while the eastern sector has a genuine marine fauna.

Pomfrets (Parastromateus niger and Stromateoides spp), croakers (Argyrosomus spp), hairtails (Trichiurus spp), and ponyfish (Leiognathus spp) occur commonly, es- pecially in autumn. A variety of isospondylous fish, such as sardines (Sardinella spp), shads (Clupanodon spp) and long-jaw herrings (Thrissa spp) may also occur in large schools seasonally. However, the Yellowtail (Seriola quinquilineata), mackerels (Scom- beromorous spp) and Yellow Croaker (Pseudosciaena crocea), which were abundant, have now diminished in stock size. The natural bays and inlets of Hong Kong also serve as nursery grounds for a number of species, notably the Long-spined Bream (Evynnis cardinalis).

From time to time dolphins may be sighted in Hong Kong waters and identifica- tions have included the Common or Saddle-back Dolphin (Delphinus delphis), the Black Finless Porpoise (Neophocaena phocaenoides) and the Chinese White Dolphin (Sotalia chinensis).

A notable marine animal which has been successfully introduced in the Deep Bay area is the Japanese Oyster (Crassostrea gigas). It is now being cultivated.

The freshwater fauna of Hong Kong is relatively poor in variety compared with the Chinese mainland. This probably results from the absence of a perpetual system of rivers and lakes. Although there are large bodies of water stored in man-made reservoirs, only a few varieties of fish life have been introduced-primarily for water quality control purposes. The indigenous fauna comprises only limited species of cyprinid, loach and goby, while the African Tilapia has also established itself in local waters, but its initial introduction cannot be traced. Despite its limited size, Hong Kong has now some 3,200 acres of commercial fish ponds, where the Grey Mullet and seven species of Chinese carp are being produced at a rate of 1.2 tons per acre per year.