A preliminary assessment of butterfly diversity from Mekhliganj town, Cooch Behar District, West Bengal, India

: In the present study, butterfly diversity from Mekhliganj town, which is located on the Teesta River bank of Cooch Behar District, West Bengal, India was studied. A total of 55 species of butterflies were recorded from the two study sites, out of which 22 species were observed for the first time from Cooch-Behar District, not recorded earlier. Out of these, five recorded species were legally protected under the Wildlife (Protection) Act (WPA), 1972 like Chliaria othona, Lampides boeticus, and Hypolimnas misippus . Therefore, efforts should be made for habitat conservation of the Teesta River bank.


INTRODUCTION
Butterflies play a number of critical roles in the maintenance of environmental quality in terrestrial ecosystems (Ghazoul 2002).Conservation biologists now utilize numerous species of butterflies to identify the important habitats that must be protected because they are highly sensitive to environmental parameters such as temperature, light, humidity, and rainfall (Spitzer et al. 1997;Thomas 2005;Bonebrake et al. 2010;Brereton et al. 2011).As an important pollinator, they face numerous conservation challenges as a result of the ongoing augmentation of anthropogenic activities such as industrialization, urbanization, usage of numerous pesticides in various agricultural, horticultural fields, deforestation along with monoculture plantation and overgrazing (Tiple et al. 2007;Roy et al. 2012Roy et al. , 2022)).
There are over 18,000 species of butterflies worldwide, out of which around 1,300 butterfly species are found in India (Samanta et al. 2017;Smetacek 2017).The northern region of West Bengal, which includes the districts of Cooch-Behar, Jalpaiguri, Darjeeling, Dakshin Dinajpur, Uttar Dinajpur, Alipurduar, Malda, and Kalimpong is well-known for its diverse fauna and flora (Pal 2017).However, very few studies of butterfly diversity from this area have been documented.
In this present study, butterfly diversity was studied in the town of Mekhliganj, which is located in the Cooch Behar District.Some authors have previously reported 66 species of butterflies from other areas of the Cooch-Behar District (Das et al. 2020;Roy et al. 2022), however, their diversity from Mekhliganj town remains undocumented and hence the present study was taken up.For this study, two geographically distinct sites were chosen.

MATERIALS AND METHODS
The butterfly diversity was studied at two geographically different study locations in the Mekhliganj city.Mekhliganj is a municipal city in Cooch Behar District located in northern part of West Bengal, covering an area of 3.88 km 2 , situated between 26.35°N and 88.92°E (Directorate of Census Operations V, West Bengal 2011).Field studies for butterfly diversity was conducted between January 2020 to August 2021.During this time each study site was visited twice a month from 0800 h to 1200 h.Butterflies were surveyed and photographed in these study areas.Butterfly survey and counting was conducted using the Pollard walk method (Pollard 1977).Butterflies were counted within 5 m on both sides of the transect walk.Photographs of butterfly specimens were taken with a NIKON D3500 DSLR camera.
Site 1: Town area (TA) consisted of ephemeral water bodies, ponds, marshes, bushes, wetlands, trees and shrubs, tea gardens and agricultural lands that are adjacent to human populations.Site 2: River bank (RB) is located in the Teesta riverbank (120-130 m from the water), and comprised of shrubs, agricultural grounds, aquatic plants and grasses as well as a few human settlements.The study area locations are listed in the Table 1 and photographs are given in the Images 1 & 2.
Three short forms were used to examine the occurrence status of each butterfly species.Butterflies that were very common and plentiful were designated as VC (more than 100), moderately abundant butterflies were designated as M (more than 30) and rare butterflies were designated as R (less than 30).Not even a single butterfly was harmed or killed during this study.
The colour patterns and wing designs of common butterflies were used to identify them on the spot.Other butterflies were carefully identified through photographs.Standard guides of entomological specialists, published literatures (Samanta et al. 2017;Mukherjee & Mondal 2020), field guide books (Smetacek 2017) and some websites (Know your insects 2022; Butterflies of India 2022) were used to confirm the identification of the butterfly species.Data analysis & all the diversity indices like Shannon Weiner index, Margalef index, and evenness index were calculated using PAST software version 4.10.

RESULTS
In the present study, a total of 55 species were recorded belonging to 44 genera of five families namely, Papilionidae, Hesperiidae, Pieridae, Lycaenidae, and Nymphalidae.Most number of species belonged to the family Nymphalidae (22 species) whereas least number of species belonged to the family Papilionidae (three species) (Image 3-5).A total of 53 species of butterflies were observed from TA whereas, 42 species were observed from RB (Table 2).
Results showed that alpha diversity of TA was little higher than the RB (comparing Shannon Weiner index).Margalef index showed higher diversity in TA (6.967) compared to RB (5.865).On the other hand, dominance was more in RB (0.05728) than TA (0.04523).Evenness index for both the study sites were close to each other.The Berger-Parker index, which indicates single taxa dominance was higher in RB (0.1454) compared to TA (0.1182).Table 5 summarises the different diversity indices of the butterflies from the two study sites.

DISCUSSIONS
As per our knowledge, this study is the first of its kind from this town and will shed some light on the region's ecosystem health and macro fauna conservation needs.Previously, three studies regarding butterfly diversity in Cooch Behar District were carried out.Thirty-three species out of a total 55 species of butterflies recorded during this study were also reported in those studies (Das et al. 2020;Roy et al. 2022).Whereas, 22 species were observed for the first time from Cooch Behar District, which were not recorded by previous authors (Das et al. 2020;Roy et al. 2022) Moreover, the number of species recorded in this study is consistent with other studies regarding butterfly diversity in various locations of West Bengal with similar landscape patterns (Ghosh & Siddique 2005;Mukherjee et al. 2015;Ghosh & Saha 2016;Mandal 2016;Mukherjee et al. 2016;Dey et al. 2017;Samanta et al. 2017;Das 2018;Pahari et al. 2018;Mahata et al. 2020;Mukherjee & Mondal 2020).The number of species recorded from the two study sites differed slightly maybe because TA was topographically more diverse than RB and also maybe TA was more suitable to support the host plants of the recorded butterfly species.
A total of five species were found to be included under the Wildlife (Protection) Act (WPA), 1972 (Table 4), viz., Chliaria othona included under schedule I and Lampides boeticus included under schedule II from family Lycaenidae; Euploea core included under schedule IV and Hypolimnas misippus included under schedule II from family Nymphalidae and Appias libythea included under schedule IV from family Pieridae.
The high diversity of butterfly fauna of Mekhliganj indicates the presence of preferable vegetation for different butterfly species.However, gradual urbanization of the town can lead to the disposal of host plants of butterflies resulting in decreased butterfly diversity.

Figure 1 .
Figure 1.Comparative abundance of recorded species among different butterfly families between Town Area (TA) and River Bank (RB).

Figure 2 .
Figure 2. Family-wise percent distribution of butterflies from Town Area (A) and River Bank (B).

Table 2 . Checklist of the butterflies reported from Mekhliganj.
VC-Very Common| M-Moderate | R-Rare.