Md. Sajjad Hossain Tuhin
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Md Kawsar Khan
Department of Biochemistry and Molecular Biology, Shahjalal University of Science and Technology, Sylhet 3114, Bangladesh
Amselflies, Dragonflies, Habitat associations, Mortonagrion varalli, Odonata, Species richness, Sundarban.
Southwestern region of Bangladesh
Pest Management
Study Site Khulna Division lies between 21.6430N to 24.1810N and 88.5610E to 89.9420E . The study area has a tropical climate with a mild winter from October to March, a hot and humid summer from March to June, and a humid, warm, rainy monsoon from June to October. Temperature varies all the year round: the temperature falls to the lowest in January and December at 12–150C and reaches the highest in April–June at 41–450C. Daily relative humidity fluctuates between 50% and 90%, which is the lowest in the evening and highest in the morning. The maximum precipitation is experienced in July with 20–25 days of rain with 368mm precipitation (Bangladesh Bureau of Statistics 2014). We conducted fieldwork in the southwestern region of Bangladesh (concentrated on Khulna Division) from August 2014 to August 2016. We surveyed eight districts (namely, Khulna, Kushita, Jessore, Bagherhat, Chuadanga, Satkhira, Magura, and Jhinaidha) and the Sundarban during the study period. We randomly selected five sites from each district, at least 2km apart, by considering the accessibility and diversity of the habitat. In total, we selected 45 sites across the entire study area. We did a regular survey (weekly, Bi-weekly, monthly, or bi-monthly) in the sampling sites (n=9) under Khulna and Jessore districts, and one or two opportunistic surveys in the rest of the sites (n=36). We recorded GPS quadrate for all surveyed sites with a GPS device (Garmin GPSMAP 76CSx). Sampling design We surveyed the odonates by walking opportunistically through the roadsides, canal banks, river banks, pond sides, lakesides, open fields, forest paths, crop fields, grasslands, and urban and semi-urban areas of the study sites from 08:00h to 17:00h. We photographed the specimens for various identification keys such as wing venation, colour, patterns of thorax and abdomen, and shape of the anal appendages with a Nikon-3200D camera using Nikkor 55–300 mm AF-S DX and Micro-Nikkor 105mm FX AF lenses. We collected specimens that were difficult to identify from visual inspection and images by using an insect sweeping net. We did not collect any endangered odonates or sample from any protected areas, hence no permission was required for the collections. We identified the odonates with the help of taxonomic keys provided by Fraser (1920, 1933, 1934, 1936), Asahina (1967), Lahiri (1987), Mitra (2002), Subramanian (2005), and Nair (2011) and classified them according to Dijkstra et al. (2013).
Journal of Threatened Taxa | www.threatenedtaxa.org | 26 December 2018 | 10 (15): 12995–13001
Journal