New butterfly species discovered in Western Ghats, researchers term it historical

Thiruvananthapuram: A new taxon of Lycaenid butterfly belonging to the Nacaduba genus has been discovered in the Western Ghats by researchers. This adds a new species to the butterfly fauna of India as well as that of the Western Ghats and Kerala as well. The common name of the butterfly has been suggested as Ramaswami’s Six Line blue and ‘Ceylon Varayanneeli’.

The discovery has been made by a team of four researchers, namely, Dr. Kalesh Sadasivan and Baiju K from Travancore Nature History Society (TNHS) Thiruvananthapuram, Rahul Khot from Bombay Natural History Society and Ramasamy Naicker from Vanam, Theni.

Line blues are small butterflies belonging to the subfamily Lycaenidae with Indo- Australian geographical range. Their distribution ranges from India and Sri Lanka, to the whole of south-eastern Asia, Australia, and Samoa. They are characterised by hairy eyes, anastomosis of veins 11 and 12 on forewings, male wings with purple gloss on the upperside, and underside of both sexes with dull whitish stripes. Males of all species have battledore-shaped specialised androconial scales and some species have long ribbon scales on the upperside of wings that gives them a frosted look.

Two individuals of line blues were photographed in 2011 from Agasthyamalais. These individuals were paler in colouration in comparison to the other Line blues that were mud-puddling with them on a damp patch on the ground. Similar pale coloured individuals were also observed and photographed at later in January 2018, and Thenkasi in Tamil Nadu in 2018. A few days later in the same month, the lifecycle was discovered on young sprouting leaves from the cut stem of Dimocarpus longan Lour (Sapindaceae).

These larvae were reared and details of the adults noted. The dissection of the genitalia of male specimens was done and they were unlike any known Nacaduba from southern India and on further investigation, they were found to match the Sri Lankan species Nacaduba sinhala Ormiston, 1924. The adults, early stages and larval host plant were similar to the Sri Lankan taxon, but the genitalia of the males was structurally different from it. This is the first confirmed record of these taxa occurring in the Western Ghats and thus the Indian mainland.

Male butterfly has its upperside violet-blue, below ground colour is greyish to ashy, markings underside larger, ribbon scales present. The underside forewing markings well showing on uppersides in males. Male genitalia unlike any other species in peninsular India. Female upperside with shiny blue restricted to the basal half of both wings, upperside forewing with rest of the pale patch white. The species appears to breed more during the northeast monsoons, though the breeding season extends from September to January, with the peak in October and the larvae are guarded by ants. As far as it is known the butterfly is known to occur only in the low elevation evergreen and mixed forests of Agasthyamalais, below the Achankovil Gap.

The new butterfly species is named after Lord Rama, signifying the connections across the sea to Sri Lanka and it may also not be a coincidence that the name has some connection to Mr Ramasamy Naiker, an avid butterfly watcher from Tamilnadu, whose persistence led to the description of this new species. This is the first record of the species N. sinhala outside its endemic range in Sri Lanka. Thus, the endemicity of the taxon is now limited to the Western Ghats complex (the Western Ghats and Sri Lanka), more specifically Agasthyamalais and Sri Lanka.

Another interesting thing to note is that this is the first time in history that a species of butterfly was discovered and described by an all Indian research team from the Western Ghats. It was either by westerners or by Japanese researchers or a collaboration of native researchers that species have been described from the Western Ghats. The last species that was discovered from the Western Ghats was the Nilgiri Grass yellow by O.Yata, a Japanese researcher in 1990 and later a subspecies of One spot grass yellow Eurema andersoni shimai by Yata and Gaonkar in 1999. Hence this is a historical find said Dr Kalesh who led the team.