New butterfly species discovered in Kerala

A group of lepidopterists has discovered a butterfly subspecies from the fringes of Akkulam and Vembanad lakes in Kerala.

A group of lepidopterists has discovered a butterfly subspecies from the fringes of Akkulam and Vembanad lakes in Kerala.

The newly-described taxon Caltoris bromus sadasiva has been discovered by Travancore Nature History Society research associate Kalesh Sadasivan in association with entomologists Dipendra Nath Basu and Krushnamegh Kunte of the National Centre for Biological Science at the Tata Institute of Fundamental Research, Bengaluru.

It is also the first record of the species Bromus swift ( Caltoris bromus), a skipper butterfly belonging to the Hesperiidae family of Lepidoptera (moths and butterflies), from the Western Ghats and Peninsular India. The finding has been published in the peer-reviewed entomology journal Entomon.

The butterfly was first spotted at Akkulam lake in 2005 and later in Vembanad in 2009 by Dr. Sadasivan, who subsequently reared the species from larvae on the host plant Phragmites karka (tall reed) to confirm the identity of the taxon. Rearing a series of larvae over a span of almost a decade was necessary to rule out another subspecies of the Bromus swift seen in Taiwan which has adults that lack any usual spots on their wings, Dr. Sadasivan said.

Caltoris, an Indo-Australian genus has over 15 species distributed across south-east Asia. Caltoris bromus, one of them, has two other subspecies Caltoris bromus bromus and Caltoris bromus yanuca.

While the various species of swift butterflies are very similar in appearance, meticulous field observation, study of the larval hosts, dissection of internal anatomy and comparisons with museum specimens are needed to identify them. The comparison of the male and female genitalia with the other Caltoris proved crucial in ascertaining its identity, according to Dr. Kunte and Dr. Basu, an expert on butterfly anatomy, who dissected the specimens to confirm the species.

The number of butterfly species in the Western Ghats rose to 336 with the discovery. The count of skipper butterflies also grew to 83 species. A skipper butterfly was last discovered nearly 75 years ago (Dakhan alida angle – Caprona alida vespa and Sahyadri common banded demon – Notocrypta paralysos mangla by lepidopterist and British Army officer W.H. Evans in 1949).