A MATHEMATICAL SIMULATION OF THERMOREGULATORY BEHAVIOR IN AN ORB-WEAVING SPIDER

1. In order to better document the thermoregulatory effectiveness of o bserved behaviours compared to other possible behaviours, we develop a model of interception of solar radiation. We demonstrate its use with data from a population of the orb-weaving spider Nephila clavipes inh abiting a mid-altitude Mexican desert. 2. Nephila clavipes exhibits th ree behaviours that appear related to thermoregulation in this extreme climate: microhabitat selection, orb-web orientation and postural adj ustments. 3. Large females more often built in open spaces without sha de and small juveniles built within shrubs in shaded web sites. Webs b uilt by large females tended to have a north-south orientation, wherea s among small juveniles there was no correlation in web orientation. 4 . Only individuals in unshaded sites exhibit postural thermoregulation , in which the spider's abdomen tracks the elevation of the sun. The s imulation revealed that interception of solar radiation by large femal es was reduced by solar tracking, but that the north-south orientation of the orb did not reduce the interception of solar radiation relativ e to an east-west orientation.