There were 42 species of butterflies in the delta region.

Environmental changes in the Cauvery delta districts of Tiruvarur and Thanjavur have become a threat to common butterflies in the region according to a research conducted by M.V. Balasubramanian, M.S. Mani Biological Association, Tiruvarur.

Dr. Balasubramanian has done his Ph.D in Butterflies Pollination Biology in the delta region and is currently a postgraduate assistant at V.S. Boys Higher Secondary School in Tiruvarur.

He also worked for six years with Zoological Survey of India.

Some of the butterflies such as Polydorus hector and Colotis calais have become less common in the region due to the conversion of river banks and fallow and cultivable lands into housing sites, Mr.Balasubramanian said.

Live fences erected in gardens, farms, and orchards have been offering food to butterfly larvae.

“Now these live fences are replaced with woven mesh and concrete that threaten butterfly habitat,” said Dr.Balasubramanian.

“There were 42 species of butterflies in the region, now species such as Polydorus hector, which used to swarm the region in December, has come down substantially,” he said. Butterflies facilitate pollination and the decreasing species count has hit flora such as leucas aspera and moringa .

Environment degradation has not spared species in hilly areas too and species such as blue mormon and neptis hylas have moved to plains. Blue mormon thrives on citrus cultivation, Dr.Balasubramanian said. He called for protection of environment, plants, and water bodies to save butterflies native to the delta.