Available online at www.worldscientificnews.com WSN 55 (2016) 210-239 EISSN 2392-2192 Rice Land inhabiting Long Jawed Orb Weavers, Tetragnatha Latreille, 1804 (Tetragnathidae: Araneae) of South 24-Parganas, West Bengal, India Debarshi Basu* and Dinendra Raychaudhuri** Department of Agricultural Biotechnology, Faculty Centre of Integrated Rural Development and Management, Ramakrishna Mission Vivekananda University, Ramakrishna Mission Ashrama, Narendrapur, Kolkata – 700 103, India *,**E-mail address: [email protected] , [email protected] ABSTRACT Spiders inhabiting rice land ecosystem demand serious consideration primarily due their predatory efficiency. In India, their role as a potential bio-control agent is yet to be evaluated. The coastal ecosystem in the Gangetic Delta at the southern part of West Bengal, India, exhibits a wide variety of predatory spider population because of climatic fluctuation, soil quality and several other factors. Orb-weaving spiders appear to be of special importance as they trap more than what they actually consume. The present study is aimed at unfolding the taxonomic diversity of Tetragnatha Latreille, 1804 (family Tetragnathidae, Menge, 1866) which is probably the mostly predominant group amongst orb-weavers found in rice fields of South 24 Parganas, West Bengal, India. Of the seven tetragnathid species recorded from the study area, three, T. chauliodus (Thorell), T. boydi O. P. - Cambridge, and T. josephi Okuma are found to be new from the country. The referred species are therefore described and illustrated. Further a key to the species occurring in the area has also been provided. Keywords: Spiders; Orb-weavers; Tetragnatha; South 24 Parganas; India World Scientific News 55 (2016) 210-239 1. INTRODUCTION Predatory importance of spiders inhabiting cultivated fields is controversial. The results of some European studies indicate that the foliage-dwelling spiders of cultivated fields, because of their low population densities, are of minor importance as predators of insects. Other European studies show, that the ground-dwelling spiders of cultivated fields are concerning their abundance, a dominant predator group, that significance as control agents still is largely unknown up to the present. In rice fields (swamp ecosystems) in Asia, receiving little or no pesticides, as well as in European and American swamp ecosystems, spiders may be an important predator group. In South Africa spiders were used successfully as biological control agents against flies. (Nyffeler and Benz, 1987) It is unfortunate that in Indian context the role of spiders as a potential bio-control agent is yet to be evaluated properly. Except a few data generated in KeralaandTamil Nadu, India, (Sebastian and Chacko,1994) and some scattered information from a few parts of this country (Chelliah, Bentur and Prakasa Rao, 1989, Gupta and Pawar, 1982, Rajendra, 1987, Banerjiet al. 1993, Ganesh Kumar, 1994, Pathak and Saha, 1999), no significant report has reached us so far. Apart from the extensive study on the predatory spiders in tea ecosystem of Dooars (Roy, 2013), an area at the foot hill of Eastern Himalaya, no significant contribution is available from the eastern region of India, especially West Bengal. However, Satpathi (2004) did emphasise the predatory potential of spiders. Success of integrating spiders in the IPM programme in any crop system largely depends on the data generated on their diversity, distribution, ecology, biology, predatory efficiency and many more. The present study therefore, is aimed at unfolding the taxonomic diversity of spiders inhabiting riceland ecosystem with special reference to Gangetic Delta. It won’t be out of place to refer the contribution of Majumder (2007) who did bring out a pictorial handbook on the spiders of Suderbans, South 24- Parganas. Interestingly, the coastal ecosystem in the Gangetic Delta at the southern part of West Bengal exhibits a wide range of species population. Climatic fluctuation and variation in soil quality induce fascinating cultural practices in this belt resulting a tremendously diverse pest upsurge at different point of time. Further, it is observed that the diversity of spidersso far encountered in this shore of Bay of Bengal shows an affinity with those of Philippines and Taiwan, which are at the other end of the Bay. Role of orb-weaving spiders should be thoroughly worked out particularly when members of this group build large webs at times. Expectedly such webs would trap more number of preys than what the spiders would actually consume.Typical orb weavers necessarily include members of the long-jawed orb weavers exclusively belonging to the family Tetragnathidae Menge, 1866, composed of 48 genera and 344 species till date. (World Spider Catalog, 2016). Significant contributors on Tetragnatha Latreille, 1804 are Okuma (1987, 1988), Barrion and Litsinger (1995), Gillespie (1987, 1991, 1992, 1993, 1994), Gillespie et. al (1997), Gillespie (2002), Dimitrov and Hormigera (2009) and Jayakumarand Sankari (2010). Genus Tetragnatha Latreille, 1804under the family Tetragnathidae Menge, 1866 especially comes under focus in our current endeavour though many others are of equal importance in the same context. Our effort so far helped record of seven speciesfromthe rice land ecosystem of South 24 Parganas, a district located at Gangetic Delta of West Bengal. Of -211- World Scientific News 55 (2016) 210-239 those, T. chauliodus (Thorell) T. boydi, O. P. - Cambridge, 1898 and T. josephi Okuma, 1988, are found to be new records from India and accordingly described and suitably illustrated supplemented by digital images. They are found to construct large horizontal web spread over the entire section of paddy fields. It thus appears that TetragnathaLatreille,1804 may be aproficient candidate of biological control, not only by devouring the prey but also by trapping more no of prey insects in their web. Following discourse is on the taxonomy of the Tetragnatha Latreillespecies recorded from the study area. 2. STUDY AREA: (vide map) Site 1: Narendrapur Site: 3 Sarisha Site 2: Arapanch Site 6: Kakdwip Site : 5 NImpith Site 7: Gosaba Site 4: Manasadwip South 24 Parganas (22.1352° N, 88.4016° E), a district of West Bengal, belongs to the large delta of the Gangetic plain. Seven discrete areas, from six different blocks are selected as fields of study. Fields in different locations are identified in such a way that they represent the spider faunal diversity of the district as a whole. Of them, three study areas are located at three different regions of Sundarban, a heritage site recognised by UNESCO in (1997 for its mangrove vegetation where due to the proximity of Bay of Bengal, salinity and nutrient structure of soil vary to a considerable extent affecting the growth and distribution pattern of the agro-ecosystems. The study areas are as follows – 1. Narendrapur [NPUR] (Block - Sonarpur) (22.4391°N and 88.3968°E), 2. Arapanch [ARPH] (Block - Sonarpur) (22.4491°N and 88.3915°E), 3. Sarisha [SRSH] (Block - Diamond Harbour) (22.1987°N and 88.2023°E), 4. Manasadwip [MSDP] (Block - Sagar) (21.753° N and 88.106°E.), 5. Nimpith [NMPT] -212- World Scientific News 55 (2016) 210-239 (Block - Jaynagar II) (22.1772°N and 88.4258°E), 6. Kakdwip [KKDP] (Block –Kakdwip) (21.8760°N and 88.1853°E), 7. Gosaba [GSBA] (Block - Gosaba) (22.1652°N and 88.8079°E) Site 1: Narendrapur Site 2: Arapanch -213- World Scientific News 55 (2016) 210-239 Site 3: Sarisha Site 4: Manasadwip -214- World Scientific News 55 (2016) 210-239 Site 5: Nimpith Site 6: Kakdwip -215- World Scientific News 55 (2016) 210-239 Site 7: Gosaba 2. 1. Time of study Field visits were carried out in every month of any calendar year during the crop seasons. It was continued form October, 2013 to November, 2015. The annual rainfall (average) in the district was 1796 mm. Temperature in the study areas varied from 10 °C to 35 °C during course of study. 3. MATERIALS & METHODS For collection of spiders, sweep nets, bush beating and collection in inverted umbrella, hand picking techniques were used. Several pit fall traps were laid in the collection localities to trap ground dwelling spiders. Samples after collection [collector: D. Basu] were preserved in 70% alcohol and later transferred to glass vials filled with Audman’s fixative. Necessary labels were used to mark each of the samples. Data regarding locality, date of collection, collector’s name were noted in a note book in the field itself. The samples were studied under Sterozoom Binocular Microscopes Olympus SZX 10 and SZX 16. Line drawings were made with the aid of necessary accessories attached to the microscopes.Photographs were taken by a digital camera attached to the microscopes. All measurements are in millimetres, made with an eye piece graticule. -216- World Scientific News 55 (2016) 210-239 3. 1. Abbreviations use TL: Total length, CL: cephalothorax length, CW: cephalothorax width, AL: abdominal length, AW: abdominal width,AME: Anterior median eye, ALE: Anterior lateral eye, PME: Posterior median eye, PLE: Posterior lateral eye. 3. 2. Deposition All materials are in the collection of Department of Agricultural Biotechnology, IRDM Faculty Centre, RKM Vivekananda University, Narendrapur. 4. TAXONOMY Members of the family Tetragnathidae Menge, 1866 have long legs and body, except in the genus Dyschiriognatha, with rounded abdomen; eyes in two rows, may be parallel or convergent but lateral eyes never contiguous; chelicerae well-developed, long, often directed forward