Another migid in the wall: natural history of the endemic and rare spider Calathotarsus simoni (Mygalomorphae: Migidae) from a hill slope in central Argentina

Abstract

A population of Calathotarsus simoni Schiapelli and Gerschman (1975) was discovered on a hillside in the Ventania system, Argentina. Our objectives were to quantify burrow density, record burrow morphology and door characteristics and describe the micro-habitat. We counted 57 burrows and report a density of 0.01 burrows/m². Aggregation indices suggest that burrows are aggregated under some area plots but more evenly distributed on others. The trapdoor is thick and rigid with bevelled edges connected to the entrance rim by a narrow articulated hinge. Two egg sacs from females were obtained and data on eggs and spiderlings are presented. We registered six burrows of an undetermined species of Actinopus. While a few specimens of Actinopus sp. were found inhabiting this hillside, the highest proportion of burrows belonged to C. simoni. Spider diversity on the hillside shows the predominance of Linyphiidae, Nemesiidae and Gnaphosidae. One juvenile of C. simoni was captured using pitfall traps.

Keywords:

• trapdoor spider
• burrow density
• aggregation
• Ventania system
• Actinopus

Acknowledgements

Special thanks are due to Pablo Goloboff for his critical reading, comments and suggestions on the manuscript. We would like to thank Mara Maldonado and the family of the “Funke” ranch for their continued hospitality and for allowing us to conduct this study. Thanks to Jorge Barneche for his invaluable help in discovering the first specimens of C. simoni. Thanks also are due to Virginia Bianchinotti (Universidad Nacional del Sur, Buenos Aires) and María Schiavone (Facultad de Ciencias Naturales e Instituto Miguel Lillo, Tucumán) for the identification of the mosses and to Georgina Zapperi for the identification of plant species. Nelson Ferretti, Sofía Copperi and Gabriel Pompozzi are supported by postdoctoral and doctoral CONICET fellowships.