New record of Dragonfly Species to Hong Kong: Emerald-banded Skimmer
2023-07-26
A dragonfly species new to Hong Kong, Cratilla lineata (Emerald-banded Skimmer; Libellulidae), has recently been recorded by an AFCD staff in Eastern New Territories. On 8th July 2023, the AFCD field staff observed a male C. lineata near a shaded stream pool in a woodland on Kowloon Peak. Cratilla lineata is a medium-sized dragonfly inhabiting pools and swampy areas in forests. The species is characterised by the metallic bluish-black frons on the creamy white face, dark brown thorax with several yellow stripes and abdomen with fine yellow stripes mid-dorsally and laterally. The yellow stripes are obscured by pruinescence in aged individuals.
Cratilla lineata has a widespread distribution over much of the Old World tropics throughout India, Sri Lanka, Myanmar, Thailand, Malaysia, Singapore, Vietnam, China, Indonesia and the Philippines. In China, it is known from Guangdong (vagrant), Guangxi, Hainan, Taiwan and Yunnan. Three subspecies have been reported. The nominate subspecies C. l. lineata is the most widespread ranging from Sri Lanka to the Philippines, while the distribution of C. l. calverti includes India and some parts of Indo-China. These two subspecies overlap in their distribution at least in Thailand (Davies and Tobin 1985; Hämäläinen and Pinratana 1999; Zhang 2019). The remaining subspecies C. l. assidua ranges from Bali and Java to the Philippines, and is also recorded in Taiwan (Lieftinck 1954; Zhang 2019). Despite some degree of geographical separation, no clear morphological difference is found between the nominate subspecies and C. l. assidua (Zhang 2019), and Fraser (1936) considered C. l. calveri to be just a late-stage maturation colour form of the nominate subspecies.
Cratilla lineata is a forest-dependent dragonfly preferring shallow pools in closed primary forests where they can be numerous, but they can also be found along forest trails (Ngiam & Ng 2022; Wilson 2020). In addition, it is a dispersive species and may be able to colonize secondary forested areas (Wilson 2020). Given the current record of Cratilla lineata in Hong Kong was a single observation, the species is therefore considered as vagrant at this stage and its status in Hong Kong awaits further observation.
Acknowledgement: We would like to thank Mr. YAM Wing-yiu for providing the record and photograph of Cratilla lineata; Dr. ZHANG Hao-miao and Mr. SONG Rui-bin for their provision of information on the distribution of the species in China.
References
Davies, D.A.L. and Tobin, P. (1985). The Dragonflies of the World: A systematic list of the extant species of Odonata. Vol. 2. Anisoptera. Rapid Communication (Supplements) No. 3. Utrecht.
Fraser, F.C. (1936). The Fauna of British India, including Ceylon and Burma. Odonata. Vol. III. London: Taylor & Francis.
Hämäläinen, M. and Pinratana, A. (1999). Atlas of the dragonflies of Thailand. Distribution maps by provinces. Bangkok: Brothers of St. Gabriel.
Lieftinck, M.A. (1954). Hand list of Malaysian Odonata. A catalogue of the dragonflies of the Malay Peninsula, Sumatra, Java and Borneo, including the adjacent small islands. Treubia (Supplement) 22: 1-202.
Ngiam, R. W. J. and Ng, M. F. C. (2022). A Photographic Field Guide to the Dragonflies & Damselflies of Singapore. Oxford: John Beaufoy Publishing.
Wilson, K.D.P. (2020). Cratilla lineata (amended version of 2011 assessment). The IUCN Red List of Threatened Species 2020: e.T167160A176225947. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T167160A176225947.en. Downloaded on 19 July 2023.
Zhang, H.M. (2019). Dragonflies and Damselflies of China. Chongqing: Chongqing University Press.
