Thermal Balance and Prey Availability: Bases for a Model Relating Web‐Site Characteristics to Spider Reproductive Success

Abstract

Analyses of the movements and web—site characteristics of the desert spider Agelenopsis apera (Gertsch) demonstrate that web locations offering the following habitat features are actively selected: shrubs, depressions, litter, and flowering herbs. A model of the effects of the thermal environment and prey avalability on the reproductive success of spiders occupying various web—site types is developed. The estimated productivity for an excellent web site (grassland depression with attractants) is 13x that determined for a poor site (larva surface). Model results suggest that more energy is to be obtained from selection of a favorable thermal environment (eight—fold difference) than from a site offering greater numbers of prey (two—fold difference). The presence of flowers at web sites increases the probability of receiving on occasional high prey density, whereas litter and habitat features providing shade (shrubs and depressions) allow increased spider activity through limitation of body temperature.