Body size aggregates multiple traits, ranging from body mass and feeding behaviour up to reproductive strategies and individual performance, and depicts the environmental fitness. Some environmental predictors like temperature can therefore be seen as multilayer factors, causing trait distribution to be multifaceted. This is remarkably evident for Ariadna Audouin (Araneae: Segestriidae) spiders, also known as corolla spiders, which were sampled at the end of the Austral Summer in the Central Namib Desert (Namibia). Here we show that these peculiar sit-and-wait spiders are able to thermoregulate behaviourally by digging until the most appropriate soil depth. This ecological process makes the actual habitat temperature at the bottom of the burrow the strongest determinant for a constant metabolic rate of soil ectotherms as computed according to the Metabolic Theory of Ecology. Keywords: Ariadna, Body mass and size, Burrows, Central Namib desert, Metabolic theory of ecology, Temperature, Trait distribution.