During a survey at Sha Tau Kok this month, Green Power’s Butterfly Surveyors discovered Hooked Oak Blue (Arhopala paramuta), and made the first official record of this species in Hong Kong, following sightings in 1981 and 1982. This record helps demonstrate that the former Frontier Closed Area of Sha Tau Kok is a butterfly hotspot, deserving conservation measures.
A Butterfly Surveyor team, led by Eric Ng Ka Leung, discovered Hooked Oak Blue on 6 July, in woodland near Sheung Tam Shui Hang, during their most recent Sha Tau Kok survey. Hooked Oak Blue belongs to the Genus Arhopala, which globally includes 200 known species of the Arhopala. Most species in the Genus Arhopala look very similar to one another; their wings are metallic brown above, and light chocolate brown with vague white wavy patterns underneath. Five species have been recorded in Hong Kong: Powdered Oak Blue, Burmese Oak Blue, Centaur Oak Blue, Dark Himalayan Oak Blue, and Hooked Oak Blue. Hooked Oak Blue is the smallest of them, and the only one lacking wing tails on the hindwings.
Hooked Oak Blue can be found in many places like southern China, India, Myanmar and Thailand. However, there have never been any photos or specimens of the species in Hong Kong; it had previously only been reported based on sight records from the northern New Territories in 1981 and 1982, mentioned in The Butterflies of Hong Kong by M. J. Bascombe. Hence it is significant that Butterfly Surveyors spotted Hooked Oak Blue at Sha Tau Kok, and took the first ever photo record of it in Hong Kong, re-discovering the species after a 32-year hiatus.
To date, Green Power’s butterfly surveyors have recorded 116 butterfly species, representing 45% of the Hong Kong total, including 9 rare species and 6 very rare species, at Sha Tau Kok. The discovery of Hooked Oak Blue serves as a further prove of the wealth of butterflies at Sha Tau Kok.
“Butterfly Surveyors” is part of the Shell Nature Watch Butterfly Explorer Scheme, launched in 2008. It is the first butterfly survey team formed by the general public and provides long-term manpower for collecting data on local butterflies. There are currently 132 qualified Butterfly Surveyors monitoring 8 butterfly hotspots: Sau Tau, Tung Chung; Luk Keng, Wu Kau Tang, Lam Tsuen (She Shan and Ng Tung Chai) and Yuen Tun Ha, Tai Po; Sham Chung & Yung Shue O, Sha Tau Kok; and this year’s new additions Pak Sha O and Lai Chi Chong on the Sai Kung Peninsula.