Within a span of five weeks, a rare butterfly species, called the Silver Forget-Me-Not (FMN), has been spotted twice inside the Srivilliputhur-Meghamalai Tiger Reserve in Virudhunagar district.
The butterfly was first sighted on September 5 inside the Srivilliputhur grizzled squirrel sanctuary, and was then seen again on October 9 near the Ayyanar Falls by a team from the Rhopalocera and Odonata Association of Rajapalayam (ROAR).
“We are thrilled to submit the first photographic evidence of the Silver FMN in Tamil Nadu,” ROAR founder Sharan Venkatesh told The Hindu . The team has been visiting the tiger reserve for the past six years to study butterfly diversity in the region.
Mr. Venkatesh sent his photographs to butterfly experts for reconfirmation, and also uploaded the images on ifoundbutterflies.org, a peer-reviewed citizen science platform. It was validated as the 318th species of butterflies found in Tamil Nadu.
The website also vetted the third sighting of the same species in Vettaiparayampalayam, Erode on October 11.
“We were lucky to stumble upon the same species twice and got photographs both of the Upper wing and close-up shots of the Underwing,” said Mr. Venkatesh.
According to Thiruvananthapuram-based butterfly expert, Kalesh Sadasivan, the species is not known to be migratory in nature. “Indigosa is its food plant and probably, the Silver FMN is overlooked due to its resemblance to the Common FMN,” he said. Both are silver in colour with a spot on the forewing. The slight variation in the discal bands, colour of the Upper wing and position of the spot determines the species.
“The common FMN is bluish-silver with a spot in the middle of its two straight discal bands. The Silver FMN is pale silvery with slightly curved bands and the spot is near the upper band,” Mr. Kalesh said, and added, “It requires a close-up view and a discerning eye to spot the difference.”
The Silver FMN was earlier recorded in Chinnar, Kerala, in 2019; in Andaman & Nicobar Islands between 2015 and 2017 and in Sikkim, West Bengal and the Northeast States of Arunachal Pradesh, Assam, Meghalaya, Mizoram and Tripura between 2005 and 2020.
In the Bombay Natural History Society’s journal, an article by T.B. Larsen titled ‘Butterflies of Nilgiris’ mentions the strange absence of the Silver FMN in South India, particularly when it was seen in abundance in Sri Lanka and South Asia till the mid-90s. Butterfly specialist Harish Gaonkar in his 1996 Compilation of ‘Butterflies of Western Ghats’ refers to the Silver FMN in Karnataka, but without photographs.