There are 114 species of dragonflies
in Hong Kong, at least 52 of which can be found in Lam
Ng Tung Chai, southwest Lam Tsuen,
spans medium to high elevations above sea level. Dragonflies
of Hong Kong's highlands are generally of low diversity,
yet the proportion of unique and rare species is relatively
high. The streams of Ng Tung Chai are clear and unpolluted,
resulting in Ng Tung Chai being home to rare dragonfly
species, such as Chinese Mountain Damsel (Calicnemia
sinensis), Yellow-spotted Shadowdamsel (Sinosticta
ogatai), Chinese Cascader (Zygonyx asahinai),
South China Shadow-emerald (Idionyx claudia)
and Yellow-spotted Dusk-hawker (Cephalaeschna klotsi).
The latter two are even unique to Ng Tung Chai.
She Shan River, a tributary of Lam Tsuen River, also
nurtures many rare dragonfly species, including Marauder
Clubtail (Labrogomphus torvus), Dog-legged
Clubtail (Burmagomphus vermicularis) and Black
Riverdarter (Onychothemis testacea), which
has only been recorded in She Shan River.
The middle course of Lam Tsuen River
is polluted. Hence the dragonfly species found here
are more resistant to pollution, such as Marsh Skimmer
(Orthetrum luzonicum) and Crimson Darter (Crocothemis