Distinctive yellow bands on a sit-and-wait predator: prey attractant or camouflage?

Many animals have conspicuous body colour that may serve physiological, camouflage or communicative functions. This study investigated the influence of bright coloration in orb-web spiders on the response of predator and prey using Argiope keyserlingi, the St Andrew's Cross spider. This species has three conspicuous yellow bands on its dorsal abdominal surface. These bands could act as camouflage devise through disruptive colouration or attract prey to the web by exploiting colour preferences in the insect visual system. In the field, naturally yellow spiders captured more prey than spiders where the yellow bands were coloured over with black marker. Similarly, some prey (Harlequin beetles: Tectocoris diophthalamus) moved towards yellow spiders and away from blackened spiders in Y-choice tests. However, native bees (Trigona carbonaria) did not seem to discriminate naturally coloured spiders at a distance when approaching a spider on a web or an empty web. Similarly, praying mantid predators (Pseudomantis albofimbriata) preferred blackened spiders over yellow spiders in a Y-maze, but they showed no preference when offered an empty web and a web occupied by a naturally coloured spider. Thus our data suggest that the main function of the conspicuous yellow bands is crypsis, perhaps via disruptive colouration that obscures the outline of the spider.