The number of butterflies seems to have reduced in the City over the years due to increasing urbanisation and pollution levels.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/butterfly-population-has-reduced-city-study
[2] http://admin.indiaenvironmentportal.org.in/category/author/bosky-khanna
[3] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-herald-bangalore
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/karnataka
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bangalore-t
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/butterflies
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/urbanisation
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/pollution
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/biodiversity