A ‘foreign’ cicada that is commonly found in several parts of South India has assumed an Indian identity.
The insect species that has now been christened Purana cheeveeda (after its Malayalam name Cheeveedu) used to be mistaken for Purana tigrina, a species that was first described in Malaysia in 1850. In view of the differences in their morphological characteristics, the Association for Advancement in Entomology has corrected the longstanding error in taxonomic identification and has excluded the Malaysian species from the South Indian cicada fauna.
The ‘discovery’ that involved correcting the mistaken identity was undertaken by a research team led by Travancore Nature History Society research associate Kalesh Sadasivan and comprising independent researchers Jebine Jose, Bernad M. Thampan, P.V. Muralimohan, Baiju Kochunarayanan, Anzil Shereef and Mick Webb of the National History Museum in the U.K.
According to Dr. Sadasivan, taxonomic studies conducted after 1850 treated the cicada seen in the region as the Malaysian species on account of superficial similarities. English entomologist Francis Walker, who presented the original description of P. tigrina in 1850, had provided only a basic account of its colouration and morphology with no illustrations or any mention of the male genitalia. Another entomologist William Lucas Distant later lumped all similar-looking insect species from Malabar, Travancore and Malaya regions in his monograph of Indian cicadas, thereby expanding the distribution of the particular taxon from South India to the Indo-Malayan sub-region.
The researchers in Kerala chanced upon the ‘discovery’ after observing differences in the structure of the male genitalia and operculum while undertaking a documentation of cicadas in the State. Their doubts were validated after the specimens were compared to the holotype and specimens of P. tigrina from Malaya that have been preserved at the NHM in London.
Suggesting the distribution of P. cheeveeda could extend across the tropical evergreen forests ranging from Goa to Kanyakumari, the researchers point out the study strengthened the possibility of cicadas being geographically and attitudinally restricted in distribution, implying a high degree of endemism. Once a common sight in homesteads, their gradual disappearance could be an indicator of the deteriorating quality of soil and vegetation, they cautioned.