Butterflies (Lepidoptera) of Dibang Valley, Mishmi Hills, Arunachal Pradesh, India
Monsoon Jyoti Gogoi
Centre for Biodiversity and Natural Resource Conservation, Department of Ecology and Environmental Science, Assam University, Silchar, Assam 788011, India
The Mishmi Hills (95049Õ–95059Õ N & 28006Õ– 28023ÕE) are located in the eastern region of Arunachal Pradesh. The altitude varies from 400–3568 m. The hill range lies to the north of the Assam Valley.
The major part of the Mishmi Hills is in the Dibang Valley districts of Arunachal Pradesh. The Dibang Valley districts have two divisions - Lower and Upper Dibang Valley. The headquarters of the two districts are Roing and Anini, respectively. Roing lies on the plains near the Lohit River while Anini is at an elevation in the mountains and near the international border with China. The valley is bounded on the north by China, on the east by Lohit District of Arunachal Pradesh, on the west by Siang District of Arunachal Pradesh and on the south by Tinsukia District of Assam. Part of the Lower Dibang Valley (281.5km2) is protected under Mehao Wildlife Sanctuary (93030Õ–95045ÕN & 28005Õ–28015ÕE) (MWS) (Image 1).
The Dibang River originates in the western part of China and flows through this valley in a north-south direction. It is one of the main tributaries of the Brahmaputra.
The vegetation is characterized by tropical evergreen forests (up to 900m), subtropical and temperate forests (900–1800 m), temperate broad leaf forest (1800–2800 m) and temperate conifer forest (2800–3500 m) (Champion & Seth 1968).
Study Area: 1. Sally Lake (Image 2): The Lake is about 5km from Roing Town and lies at an altitude of about 400m. The lake is very close to the Deopani River and is surrounded by hills. Small streams flow through the bamboo forest into the open areas. The lake is protected under MWS.
2. Deopani River Bed: The river bed remains dry throughout the year. The river gets its water from the streams originating in the surrounding hills near Deopani. High elevation forest exists in this area. The plains have secondary forest growth.
3. Dibang River-bed (Image 3): It lies west of the Mishmi Hills and is not under the jurisdiction of MSW. There are several small villages like Chidu. The vast grassland of Nizamghat (elevation of 266m) is in this area.
4. Tiwarigaon (Image 4a): A small village on the way to Mayodia, lying at an elevation of around 1300m. The place is the perfect place for the study of high montane butterflies and is 28km from Roing Town.
5. Mayodia pass (Image 4b): The area lies on the way to Anini and is about 56km from Roing Town. This area is the highest elevated point on the way from Roing-Hunli at 2,666m and is distinguished by a cold rocky mountain.
The methodology involved checklist surveys on sunny days from 07 March–22 June, 2011 to determine the maximum number of species. Visual search and photography were conducted on a regular basis during the day. Occasional surveys were undertaken after 16:00hr to locate shade loving butterflies. Searches were conducted near water sources, damp patches in the forest, open sunny areas, blossoming flowers and bird droppings. Searches were also conducted on hill tops, especially in the catchment areas of hill streams, as well as from top to bottom of hill streams to record the maximum number of species. Butterflies were photographed from different angles as often as possible to obtain sufficient photographs to enable positive identification of species. Butterfly species were identified using the identification keys of Watson (1897), Evans (1932), Talbot (1947), Smith (1994), Pinratana (1985), Haribal (1992), and photographic guides of Kehimkar (2008).
Results and Discussion
The field study resulted in the recording of 294 butterfly species belonging to 156 genera, from Dibang Valley (Table 1). This includes 33 species of Papilionidae, 26 species of Pieridae, 59 species of Lycaenidae, 115 species of Nymphalidae and 61 species belonging to Hesperiidae. Noteworthy rare and endangered species encountered were de NicŽvilleÕs Windmill Byasa polla which is included on Schedule I of the Indian Wildlife (Protection) Act (IWPA), (1972); Khaki Silverline Spindasis rukmini is another interesting species which is also included on Schedule I of the IWPA, (1972).
The matter of greatest concern is that Byasa polla, Spindasis rukmini were recorded outside the protected area of MWS. The species were recorded in a small village called Chidu near Nizamghat. The area is undergoing deforestation due to increase of settlements in the area and clearing of land for agriculture. Logging has also been observed on a small scale in the area. The increasing use of pesticides in the citrus orchards is another concern in the area. Overall, the last remaining lowland forest of Lower Dibang Valley is facing a serious threat to its continued existence at present. All these raise serious concerns regarding the survival of butterflies in the area. The record of such rare species in the area shows the potential biodiversity of the area and reflects the need for notification of more protected areas in Arunachal Pradesh.
It is stressed that the present survey covered the period from March–June 2011. Doubtless, there will be numerous additions to the following list when surveys are conducted at other seasons. Also, much of the study was concentrated in and around Dibang River bed, the lowest altitude of Mishmi Hills. Very little survey was done between Tiwarigaon (1,300m) and Mayodia Pass (2,666m), proper survey in this area will yield more species.
© All photos by Monsoon J. Gogoi, except for Image 33, which is by Rajib R Tariang.
Champion H.G. & S.K. Seth (1968). A Revised Survey of the Forest Types of India. The Manager of Publucations. Government of India, New Delhi, 404pp.
Evans, W.H. (1932). The Identification of Indian Butterflies—2nd Edition. Bombay Natural History Society, Mumbai, India, 464pp+32pl.
Haribal, M. (1992) The Butterflies of Sikkim Himalaya. Sikkim Nature Conservation Foundation, Sikkim, India. 217pp.
Kehimkar, I. (2008). The Book of Indian Butterflies. Bombay Natural History Society and Oxford University Press, Mumbai, India, 497pp.
Smith, C. (1994). Butterflies of Nepal. Tecpress Services L.P., Bangkok, Thailand, 368pp.
Talbot, G. (1947). The Fauna of British India, including Ceylon and Burma: Butterflies, Vol. II. Taylor and Francis, London. 506pp.
Watson, E.Y. (1897). Hesperiidae Indicae : being a reprint of descriptions of the Hesperiidae of India, Burma, and Ceylon. Madras Staff Corps, Vest and Company Mount Road, Madras, 161pp.