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.