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New sub-species of six-line blue butterfly discovered from south Western Ghats

One of the authors says that this was the first time a new species was discovered by an all-Indian research team from the Western Ghats.

A new sub-species of the six line blue butterfly named Nacaduba sinhala ramaswamii has been discovered from the south Western Ghats and it adds to the butterfly fauna of India as well as that of the Western Ghats of Tamil Nadu and Kerala. Four researchers – Kalesh Sadasivan and K. Baiju from Travancore Nature History Society (TNHS), Rahul Khot from Bombay Natural History Society (BNHS) and S. Ramasamy Kamaya Naicker of Vanam in Theni described the species. It was published in the Journal of Threatened Taxa in March, 2021.

The new butterfly species is named after Lord Rama, signifying the connection across the sea to Sri Lanka. It is also a coincidence that the one of the authors whose efforts led to the discovery is named Ramasamy, an avid butterfly watcher from Tamil Nadu, whose joint efforts resulted in description of the new taxa. This Lycaenid butterfly belongs to Nacaduba genus and its common name is Ramaswami’s Six Lineblue and Ceylon Varayanneeli in its vernacular.

“It was first photographed in 2011 by Dr. Kalesh Sadasivan from Kerala and later in 2015 and 2018 in Tamil Nadu. It took so long to differentiate it from other species of Nacaduba that occur here due to the complexity of this small group,” said Mr. Ramaswamy

He also added that this was the first time a new species was discovered by an all-Indian research team from the Western Ghats. New species in the past were discovered by the British or Japanese researchers or in collaboration with native researchers,” Mr. Ramasamy explained.

The research team investigated the leaves of the Dimocarpus longon, the host plant of the butterfly from various states of egg to final instar larvae. The larvae were reared and details of adulthood noted. The dissection of genitalia of the male revealed that they were unlike any known Nacaduba from South India.

“On further investigation they were found matching the Sri Lankan species Nacaduba sinhala Ormiston. But the genitalia of the male was structurally different from it. This is the first confirmed record of this taxa occurring in the Western Ghats and thus the Indian mainland,” the journal explained.

The distribution of line blues butterflies range from India and Sri Lanka, to the whole of southeastern Asia, Australia and Samoa. They have hairy eyes, anastomosis of veins 11 and 12 on forewings, male wings with purple gloss on the upper side, and upper side of the both sexes with dull whitish striae.

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