First record of Banded Lineblue Prosotas aluta Druce, 1873 (Insecta: Lepidoptera: Lycaenidae) from Bangladesh

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The Kaptai National Park (KNP) situated at Kaptai Upazila (sub-district) in Rangamati District falls between the Karnaphuly River and Kaptai mountain ranges (22.5 0 N and 92.33 0 E) (Figure 1). It is about 57km north of Chattogram (Chittagong) City and 12km south of Rangamati Town comprising an area of 54.64km² (5,464ha, 13,502acres). The park was previously known as Sitapahar Reserve and was declared a national park in 1999. It comprises two forest ranges: Kaptai and Karnaphuli. The KNP is sub-tropical mixed evergreen forest decked with hills, streams, valleys and plain lands. The area in the landscape context is very good, but disturbed by shifting cultivation, secondary plantation and human settlement. Nonetheless, the KNP is very rich in flora and fauna. The area is known as a butterfly hotspot in Bangladesh (Habib et al. 2016).
The survey was conducted on butterfly diversity twice a month from January 2017 to December 2018. As the study was carried out on butterfly diversity hence emphasis was given on sunny periods of the day, when J TT butterflies are more active. Butterflies were searched for through the existing roads, trails, streams and bridle paths.
The observed butterfly was photographed but the specimen neither killed nor collected. So, the specimen was identified based on photographic document following the keys developed by Bingham (1907) and field guides (Chowdhury & Hossain 2013;Kehimkar 2013).
An individual of Prosotas aluta (Image 1) was found at about 11:50AM (GMT+6) on 07 September 2018 in a hill stream named 'Baro Chara' (22.501 0 N & 92.184 0 E, 9m). The butterfly was puddling on small hilly rocks and sandy clay. The observed individual is characterized by the tail in the hind wing like other lycaenid butterflies (Kehimkar 2013). Moreover, shiny silky brown cilia, brown tails with white tip, black head and antennae, bluish thorax and abdomen indicate that the photographed specimen is a species under the genus Prosotas (Bingham 1907). The specimen is also characterized with dark brown under wings, spaces between discal lines filled with dark bands in both wings, and discal band and end cell band joined together to form a black discal area in the underside of hind wing (Kehimkar 2013). In addition, sub-basal and discal bands in the underside of hind wing inwardly and outwardly edged with slender white lines and discal band greatly broad in the middle (Bingham 1907).
Previously the species was recorded from Cachar and Khasi Hills (Parsons & Cantlie 1948) of India which is close to Bangladesh. So, Larsen (2004) listed the species in a possible checklist of butterflies in Bangladesh. The species has also been recorded from the Baghmara National Park of Garo Hills in Meghalya (Kunte et al. 2012) and from Jeypore-Dehing Forest in Assam of India (Gogoi 2013). Subsequently, the species has been recorded from the Kaptai National Park of Bangladesh (aerial distance: ~266km from Cachar, ~330Km from Garo Hills, ~367km J TT from Khasi Hills and ~575km from Jeypore-Dehing Forest). The northeastern region (greater Sylhet) of Bangladesh also comprises some mixed evergreen forested areas similar to KNP. In addition, the northeastern part is closer to the Cachar, Garo Hills, Khasi Hills and Jeypore-Dehing Forest (aerial distance: ~112km, ~124km, ~164km and ~413km respectively). So, the species may also be found in the northeastern mixed evergreen forests of Bangladesh. The record of Prosotas aluta, however, confirms its existence in Bangladesh after the compilation of butterflies by Larsen (2004) and Red List of Threatened Species (butterfly) by IUCN Bangladesh (2015).