Ontogenetic and Seasonal Changes in Webs and Websites of a Desert Widow Spider

Morphometric and nest position variables were used to examine the effects of spider growth and seasonality on webs and websites of the desert widow spider, Latrodectus revivensis Shulov (Theridiidae) in the Negev desert of Israel. The form of the web was similar over the full range of spider body sizes. All morphometric variables had strong positive correlations with spider size: larger spiders occupied larger nests in larger shrubs. However, nest characteristics were more highly correlated with spider size than were website characteristics. When the effect of spider size was removed by regression, more than 75% of the remaining variance consisted of correlated variation in three groups of variables relating to (1) website characteristics (48%), (2) nest characteristics (18%) and (3) capture web placement (12%). Most nest and website variables showed effects of seasonality that were independent of spider size, and may be related to the thermal regime in the nest. The results indicate that the relative quality of potential websites changes seasonally and with spider growth. We suggest that the costs of relocating a web outweigh the advantages of reaching a new website, with the result that spiders remain for some time in websites which have become less suitable.