Arachnologische Mitteilungen 58

98 O. M. Drisya-Mohan, N. A. Kashmeera & A. V. Sudhikumar predator. Previous studies described the influence of coope- ration on the predatory efficiency of social spiders ( Jackson 1979, Krafft 1970, Pasquet & Krafft 1992, Guevara & Avilés 2011,Majer et al. 2018). In Anelosimus , there is a tendency for social species to capture larger prey (Nentwig 1985, Avilés et al. 2007, Guevara et al. 2011). For Stegodyphus the effects are less strong and with increasing group size, per capita foraging rate decreases (Majer et al. 2018).However, more information is needed on cooperation, predatory efficiency and the nature and size of the prey captured in other species in the genus Stegodyphus (Eresidae). In the present study, characteristics of spider cooperation were studied in the Indian cooperative spider Stegodyphus sarasinorum (Karsch, 1892), which is one of three permanently cooperative species in the genus Stegody- phus (Kraus & Kraus 1988). Individuals live in large coopera- tively built colonies with a nest or retreat and a sheet web for prey capture ( Jackson & Josephs 1973).The aim of this study was to analyse the efficiency and prey immobilizing characte- ristics of cooperative prey capture under natural conditions in relation to the type and size of the captured prey. Material and methods Study organism and site Stegodyphus sarasinorum Karsch, 1892 (Eresidae), is a per- manent social spider found in India, Sri Lanka, Nepal and Myanmar (Kraus & Kraus 1988, WSC 2019). It makes large complex silk nest of variable sizes on bushes, shrubs, rocky areas and open fields, where flying insects are abundant (Bra- doo 1972) . The nest is placed in trees and shrubs or someti- mes fences, and made by incorporating the structure, leaves, branches, prey remnants and also their own exuviae into the silk nest. The site identified for the study was on the Christ College campus (10.350°N, 76.200°E, 12 m a.s.l., Fig.1a), lo- cated in the town of Irinjalakuda in the Thrissur district in Kerala.The study was undertaken during the period of June– September 2017. The observations were made in the field (Fig. 1b-d). Methods Natural prey of S. sarasinorum . The natural prey was identi- fied by examining prey remnants (wings, cuticle, mouthparts, etc.) from the nest.We sampled 30 nests for the identification of the natural prey types. Observations were repeated 3 times Fig. 1: a. Map of the study area at Christ College, Irinjalakuda (red spots = social spider web colonies); b. distribution of colony in Eugenia uniflora ; c. an individual colony of S. sarasinorum ; d. immobilization of the prey