Ecology and Behavior of the Giant Wood Spider in New Guinea
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Ecology and Behavior of the Giant Wood Spider Nephila maculata (Fabricius) in New Guinea MICHAEL H. ROBINSON and BARBARA ROBINSON SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 149 SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION The emphasis upon publications as a means of diffusing knowledge was expressed by the first Secretary of the Smithsonian Institution. In his formal plan for the Insti- tution, Joseph Henry articulated a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the Smithsonian imprint, com- mencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Annals of Flight Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Studies in History and Technology In these series, the Institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of professional colleagues at other institutions of learning. These papers report newly acquired facts, synoptic interpretations of data, or original theory in specialized fields. These pub- lications are distributed by mailing lists to libraries, laboratories, and other interested institutions and specialists throughout the world. Individual copies may be obtained from the Smithsonian Institution Press as long as stocks are available. S. DILLON RIPLEY Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 149 jicology and Behavior of the Giant Wood Spider Nephila maculata (Fabricius) in New Guinea Michael H. Robinson and Barbara Robinson SMITHSONIAN INSTITUTION PRESS City of Washington 1973 ABSTRACT Robinson, Michael H., and Barbara Robinson. Ecology and Behavior of the Giant Wood Spider Nephila maculata (Fabricius) in New Guinea. Smithsonian Contributions to Zoology, number 149, 76 pages, 30 figures, 11 tables, 1973.-— Investigations of the seasonal, reproductive, and population ecology of Nephila maculata are reported in detail. In an investigation of feeding ecology over a one-year period, the discarded remains of the prey caught by a sample population of ten adult female spiders were collected daily. These remains were identified (where possible) and the accumulated weekly discards from each spider were dried and weighed. Data from this study are analyzed, tabulated, and compared with the catches from insect traps located in the study area. The study included an investigation of web structure, frequency of web renewal, and the number of kleptoparasites associated with Nephila maculata. Studies of behavior included courtship, mating, predatory behavior, and responses to predators, sunlight, and rainfall. Courtship behavior included a complex pattern of silk deposition by the male on the female, here reported for the first time for the Araneida. The predatory behavior of N. maculaia is analyzed in terms of behavior units and behavior sequences and is compared with that of other Nephila species, related species, and that of other araneids studied by the authors. The phenological aspects of the study are stressed and discussed. OFFICIAL PUBLICATION DATE is handstamged jji a limited .number of initial copies and is recorded in the Institution's annual report, Sm^tnsonian Year. SI PRESS NUMBER 4779. SERIES COVER DESICN: The coral Montastrea cavemosa (Linnaeus). Library of Congress Cataloging in Publication Data Robinson, Michael H. Ecology and behavior of the giant wood spider Nephila maculata (Fabricius) in New Guinea. (Smithsonian contributions to zoology, no. 149) Bibliography: p. 1. Nephila maculata—Behavior. 2. Spiders—New Guinea. I. Robinson, Barbara, 1931— joint author. II. Title. III. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 149. QL1.S54 no. 149 [QL458.A65] 591'.08s [595'.44] 75-1905 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price $1.45 (paper cover) Contents Page Introduction 1 The Species 2 Techniques of Study 3 The Study Area 7 Natural History and Ecology 7 Web Studies 7 Web Location 7 Web Structure 8 Web Renewal 10 Web Strength 12 Reproduction 12 Males on Webs of Females 12 Egg-laying . 13 Hatchling Behavior and Dispersion 14 Phenology of Population Increments 15 Prey and Prey Captures 17 Taxonomic Range . 17 Numbers in Taxa 17 Temporal Distribution . 19 Weights of Prey Remnants 21 Comparison with Argiopc argentata 23 Comparison with Insect-Trap Catches 24 Rejections of Trapped Insects 27 Kleptoparasites 29 Numbers and Nature 29 Activities 30 Colonization of Host Webs 32 General Considerations 32 Energetics 33 Phenology 33 Behavior . 34 Terminology 34 Sexual Behavior 34 Finding the Female 34 Courtship 35 Copulation 41 Discussion 41 Predatory Behavior 44 Behavior Units of Nephila maculata 44 Behavior Units of Other Species 52 Behavior Sequences 54 Comparison with Argiope aemula . 59 Comparison with Nephila clavipcs 60 iii Page Categorization of Araneids by Predatory Behavior 62 Behavior of Prey in the Web . 63 Responses to Environmental Factors 64 Defensive and Escape Behavior . 66 Discussion 67 Phenology .. 67 Behavior 69 Literature Cited 70 Appendix 1: Activities of Male Nephila maculata during Courtship Silk-deposition 73 Appendix 2: Verbatim Notes on Selected Sequences Given to Large Acridiids 75 Ecology and Behavior of the Giant Wood Spider Nephila maculata (Fabricius) in New Guinea Michael H. Robinson and Barbara Robinson Introduction accounts of the natural history of Nephila maculata (Fabricius) in India. Bonnet (1929), Coleman Araneid spiders belonging to the genus Nephila (1948), Gerhardt (1930), Jager (1960), and Mc- form a conspicuous element of the invertebrate Keown (1963) have written on various aspects of faunas of both the Old and New World tropics. the behavior or ecology of other Nephila species. In addition, they extend into north and south tem- Peters (1954, 1955) studied the web construction of perate regions. The adult females of most species Nephila clavipes (L.). are large and build strong webs of golden silk that Studies of the predatory behavior of Nephila are often of considerable size. McKeown (1963) clavipes in Panama (Robinson and Mirick, 1971) cites examples of Nephila species catching and con- suming small birds and also mentions that the led to the conclusion that this species was primitive natives of the South Pacific use the webs for catch- (Robinson, Mirick, and Turner, 1969). At this ing fish. An interesting account of the use of stage we thought that a more comprehensive study Nephila silk for fishing appears in a work of fiction of a Nephila species would be worthwhile and by Olaf Ruhen, a New Zealander with wide exper- rewarding. We were able to make some observa- ience of the Pacific region. He states (1969:64) tions on Nephila and related Nephilengys species that the web is matted into a wad the size of a in West Africa during February and March 1970, human thumb and flown over the surface of the and further observations on Nephila and Nephi- sea suspended from a kite. There it is seized by lengys in Madagascar and on Nephila and Herennia garfish which are unable to disentangle their teeth in India (March/April 1970). In New Guinea we from the silk and are caught. Surprisingly there found that Nephila maculata was abundant in the have been few studies of the biology of Nephila Wau valley (Morobe District) where we were to species and attention has largely centered on the spend one year at the Wau Ecology Institute. The taxonomy and zoogeography of this group. Fischer spiders living in the arboretum of this institute (1910a, b, c), Hingston (1922a, b, c; 1923), and were protected from disturbance and we decided to Thakur and Tembe (1956) have published short make a long-term field and laboratory study of this species. Michael H. Robinson and Barbara Robinson, Smithsonian Tropical Research Institute, Post Office Box 2072, Balboa, This paper is based on our studies in New Canal Zone, Panama. Guinea but also includes comparative data from SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY the observations carried out in West Africa, Mad- paper. In particular we are grateful to Dr. A. S. agascar, and India, and unpublished data from the Rand and Dr. H. Wolda for advice and help with study carried out by Robinson and Mirick in Pan- the analysis of data. ama. The New Guinea studies were basically ecological and behavioral. Ecological studies in THE SPECIES eluded observations on web structure and habitat, sampling of potential and actual prey, phenological Fr. Chrysanthus identified the Wau material as studies of reproduction and predation, investigation Nephila maculata. The species has reportedly a of population numbers of kleptoparasites, and wide distribution in the Old World tropics and recording population fluctuations of adult and im- subtropics (Roewer, 1942; Bonnet, 1958). Roewer mature Nephila. The behavioral studies were main- (1942:929) gives the distribution as "Ceylon, Indien ly concentrated on predatory behavior but also bis China u. Australien," while Bonnet (1958: included