Butterfly surveyors conducted survey in May and Angled Red Forester (Lethe chandica) was discovered. The species was first recorded in Hong Kong in late 2011. Although there were sporadic reports in early 2012, they were restricted to a small area, at Tai Po Kau and Wu Kau Tang. The discovery in Sha Tau Kok furthered our understanding of their distribution in Hong Kong while revealing the rich butterfly resources in the area.
There are four species of Genus Lethe locally, including Banded Tree Brown (Lethe confusa), Straight-banded Tree Brown (Lethe verma), Bamboo Tree Brown (Lethe europa) and Common Tree Brown (Lethe rohria). Their common feature is the white band on the forewings. Angled Red Forester is a new member of Genus Lethe in Hong Kong, making the total number of species in Genus Lethe from four to five.
Ecological corridor to enhance species movement
Angled Red Forester is mainly distributed across Southeast Asia and Southern China, reaching as far as Taiwan, Thailand, Myanmar, the Philippines and India. It is widely distributed in China, including Guangdong, Guangxi, Fujian, Chejiang, Yunnan and Tibet. Its appearance in Hong Kong may be a result of natural migration, or its caterpillars being introduced with imported plants, or adults flying with monsoon winds.
Green Power proposed that Sha Tau Kok be developed into a green corridor, and ecotourism should be strongly promoted. The government must protect Sha Tau Kok habitats with high ecological value and special scientific interest as soon as possible. At present, Angled Red Forester is found in Tai Po Kau, Wu Kau Tang and Sha Tau Kok. The three sites are connected geographically, proving the importance of "ecological corridor" in facilitating species migration. Sha Tau Kok is next to Robin's Nest, which is in turns connected to Pat Sin Leng, Tai Po, and Wutong Mountain in mainland China, forming an 5,600-hectare ecological corridor. Preservation of Sha Tau Kok can enhance the movements of species between Hong Kong and China. Green Power recommended that the government designate the woodland connecting Sha Tau Kok to Robin's Nest as a conservation area or a Site of Special Scientific Interest, to act as a buffer zone between Sha Tau Kok villages and the proposed Robin's Nest Country Park.
Ecological surveys help justification for conservation
Apart from Angled Red Forester, the butterfly surveyors also recorded 69 butterfly species, including five rare species and 2 very rare species. Pigmy Scrub Hopper (Aeromachus pygmaeus), Red-breast Jezebel (Delias acalis) are rare species and are narrowly distributed locally. The former is also the smallest butterfly in Hong Kong.
Although Sha Tau Kok is proofed to have rich butterfly resources, it is already facing immense development pressure following opening up in February 2012. The situation regarding butterfly ecology is worrying. In fact, a variety of rural developments such as small houses, housing estates, leisure farms, war game fields and parking lots are threatening the natural habitats in the area. Butterfly surveys collect ecological data to fill up the blank left during the closing period, and on the other hand, provide justification for conservation in long term.