A Note on Annual Bidirectional Movement of Butterflies at South-Eastern Plains of India

North-South bidirectional migration of butterflies was seen at coastal areas of Kalpakkam in the months of October and July respectively. A 10 meter wide imaginary strip was chosen to assess the swarm density. The migration was huge during October (2009) and relatively less in July (2010). Migratory swarm was comprised of three species viz., Catopsilia pyranthe, Catopsilia pomona and Papilio demoleus. Totally 34,556 individuals were observed. In the swarm, C. pyranthe and P. demoleus constituted 86% of the total count. The activity of migratory swarms increased during the peak day hours (12.00 to 13.30 hr), but the movement was varied between seasons. The daily migratory activity appears to be shaped by temperature. However the existence of an endogenous control cannot be overruled. We believe that this migration is not only the rain avoidance movement but also to avoid competition at the site of emergence and to utilize the availability of larval host plant resources at the destination site.