RESEARCH ARTICLE

DIVERSITY AND MORPHOMETRY OF ORB WEAVER SPIDERS IN RAINFORESTS IN SRI LANKA

Abstract

Web building spiders in Sri Lanka are a poorly studied group of arachnids. Documenting spider communities assume importance in the view of current threats of habitat loss and degradation of the southwestern rainforests. Here we report the findings of a survey of orb web spiders inhabiting selected low to mid elevation rainforests in Sri Lanka. The study was carried out in seven reserves, namely Kanneliya, Kombala-Kottawa, Yagirala, Meethirigala, Runakanda, Bodhinagala and Indikada Mukalana, each located within one of four districts, Galle, Kalutara, Colombo and Gampaha. The study was conducted over the period February to December, 2016. A total of 150 transects, each 100 m in length, were surveyed in core areas and in the fringes of these forests.

The recorded 232 orb weaver spiders belonged to eleven genera in three families. A total of nine species and seven possible morpho-species were identified: Family Araneidae - seven species and three morpho-species in seven genera, Family Nephilidae - one species and Family Tetragnathidae – one species and four morpho-species in three genera. All recorded species were native with none being endemic. The confirmed species were Argiope aemula, A. aetherea, Cyclosa bifida, Eriovixia laglaizei, Gasteracantha geminata, Neogea nocticolor, Parawixia dehaani, Nephlila pilipes and Opadometa fastigata while the morpho-species were of the genera Neoscona, Tetragnatha and Tylorida. Neogea nocticolor is a critically endangered species while Nephila pilipes is a near threatened species. Some species (N. pilpes and O. fastigata) were relatively abundant while E. laglaizei, Neogea noticolor and P. dehani recorded only a single individual. Occurrence patterns differed between species some being restricted to single forests. The Indikada Mukalana forest was seen to be the richest in terms of species. The encountered orb weavers varied remarkably in their morphometry with the largest spider Nephila pilipes having a body length (i.e. cephalothorax length + abdomen length) of 20.4 mm, whilst the smallest Neoscona Sp.1 being only 4.1 mm in length.

This study has generated preliminary information on abundance and distribution of the orb web spiders in rainforest habitats that would allow better assessments of the conservation status of this sparsely studied group of arachnids.

Keywords: orb weave spiders, rainforests, Nephila pilipes, morphometry

How to Cite: Tharanga,D,Wijerathna,T,Wijesinghe,M.R, (2017). DIVERSITY AND MORPHOMETRY OF ORB WEAVER SPIDERS IN RAINFORESTS IN SRI LANKA.WILDLANKA, 5(1):Pages 017-026

Published On:2017-05-31

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