COMPARATIVE ANALYSIS OF THE LOCAL BUTTERFLY DIVERSITY IN AND AROUND SOUTH KOLKATA WITH THE GROWING POLLUTION LEVEL

摘要

Butterflies are known to contributesubstantially to the growth, maintenance and expansion of flora. Butterflies havealways fascinated humankind. Among insects, they are certainly the most popular and best-known group, and that is probably why they are among the most studied insects.Pollution has been a major threat to the survival of many speciesof living organisms on the earth since the beginning of industrialization. However, Kolkata and its suburban areas werenot much hampered as lately as the dawn of the 21th century when the pollution levels in and around the city started reaching alarming levels.So,we carried out a study concerning the butterflies in and around South Kolkata with a view to record the species richness and abundance of different butterfly species in different seasons and to analyze the effect of pollutants (SO2, NO(2)and PM10) on them.A total of 1255 specimens of butterflies were counted in a year-long census from the study sites. These belonged to 49 species under 33 genera and 4 families [Papilionidae (6 species), Pieridae (9 species), Lycaenidae(11 species) and Nymphalidae (23 species)]. Family Hesperiidaeis excluded due to problem in spot identification at field.Analyzing the collected data it is concludedthat in post-monsoon season overall butterfly diversity increases whereas in pre-monsoon season some specific species of butterflies flourish than that of others thereby increasing the dominance.The collected data indicated that although the pollution level is increasing and has affected the population in few sampling areas,the effect of pollution is not pronounced enough to unsettle the adult butterfly population in and around South Kolkata. Thus,the main reason of decreasing number of butterflies is not increasing air pollution but due to habitat destruction by natural or anthropogenic cause