第 35 卷 第4 报 Vol. 35, No.4 2011 7 ACTA HYDROBIOLOGICA SINICA July, 2 0 1 1 Received Date: 2010-06-12; Accepted date: 2011-01-26 Corresponding author: Dr. S. Anbalagan, E-mail: anbumdu@gmail.com DOI: 10.3724/SP.J.1035.2011.00688 EFFECT OF TOURISM ON THE DISTRIBUTION OF LARVAL BLACKFLIES (DIPTERA: SIMULIUM) IN PALNI HILLS OF SOUTH INDIA Sankarappan Anbalagan 1 , Sundaram Dinakaran 2 , Jeyaraj Pandiarajan 1 and Muthukalingan Krishnan 1 (1. Department of Environmental Biotechnology, Bharathidasan University, Tiruchirappalli-620024, Tamil Nadu, India; 2. Centre for Research in Aquatic Entomology, The Madura College, Madurai-625016, Tamil Nadu, India) Abstract: The effect of tourism on the distribution of larval blackflies during three different seasons of Palni hills was investigated. Six streams were selected (Kumbakkarai, Moolayar, Kurusedi, Silver cascade Pampar and Guntar) for this study, of which, three streams (Silver cascade Pampar and Guntar) were in peak of Palni hills (Kodaikanal town areas) and easy access to the tourists. The remaining three streams (Kumbakkarai, Moolayar and Kurusedi) were in downhill areas. The physico-chemical and stream parameters analyses indicated that the most tourist accessible site of Silver cas- cade stream had poor water quality and the predominant of larval blackfly population when compared to other sampling streams. The highest population of larval blackflies was observed during winter followed by summer and northeast monsoon. Since the effect of tourism causes pollution to streams, which in turn to promote the population of blackfly larvae and affect the other insect community in streams. Key words: Tourism; Simulium; Distribution; Seasonality; Onchocerciasis CLC number: Q143 + .4 Document code: A Article ID: 1000-3207(2011)04-0688-05 As the first world congress on ecotourism held at Rio-de Janeiro, ecotourism play an important integral part in a country’s economic development and there are urgent needs to study the impacts on nature. In India, ecotourism is budding as a key sector in the economy and it offers employment for innate people. Although ecotourism has proved to be an engine of growth in In- dian economy, impacts on environment still requires se- rious attention. Since stream invertebrates act as a buffer for stream ecosystem and links terrestrial and aquatic ecosystem, it is essential to monitor and conserve the stream invertebrates. Adult black flies are small insects and deposit eggs from 200 to 800 per female. Larvae emerge from eggs and attach themselves to aquatic or emergent vegetation as well as rocks. Most black fly larvae are filter feeders, with the larvae feeding on nu- trients in the water as it flows by. Larvae pass through six stages before reaching the pupal stage. Pupae are encased in a silken cocoon attached to vegetation or other objects in the stream. Adults emerge from the pupal case through a slit and float to the surface on a bubble of air [1] . The length of the cycle from egg to adult is vari- able, depending on the black fly species and water tem- perature. The time interval for Simulium species in south India is estimated to be from three to four weeks and nine cohort interval per annum [2] . Among stream invertebrates, the larval blackfly species (Simulium) constitute a vital component and are employed as bioindicators of quality of aquatic habitats due to high sensitivity to environmental degradation. Larval habitats for black flies primarily consist of swift running water, with shallow mountain torrents being fa- vored places [3] . In land, adult female black flies cause the disease of Onchocerciasis for human, which is common in Africa. Moreover, female blackfly bites may become itchy and swollen in human body for a number of days [4] . In sensitized individuals reaction to black fly saliva in- jected at the feeding site may cause a syndrome known as “black fly fever” that consists of headaches, fever, nausea, and/or inflammation of nymph nodes [3] . Numer- ous works have been carried out in environmental effects on macroinvertebrates community in world but few studies of tourist’s effects on macroinvertebrates have been received recently, for example, anthropogenic im- pact, habitat quality, effect of environmental variables etc. [5—7] . Though blackfly species as a vector, there are no more study on blackfly species with anthropogenic perturbations in India. Therefore, the objective of the