Web-decorating Sequences by the Spider Argiope luzona (Walckenaer, 1841).

Many orb-web weaving spiders add highly visible zigzagging silk "decorations" to their webs that are thought to function in prey attraction or predator avoidance. Despite the long history of studies on the form, frequency, and function of these structures, little attention has been paid to their mode of construction. Here, we report for the first time the sequence of construction of decorations by Argiope luzona (Walckenaer, 1841), a common species in the northern Philippines. A disc-shaped decoration built by a juvenile was laid as several continuous loops in a modified figure-eight pattern. The resulting asymmetric design is typical of many Argiope spp., hence suggesting that disc decorations are built similarly across the genus. In a full cruciate decoration of an adult female spider -- consisting of four diagonal arms arrayed around the web's hub -- each two-armed diagonal was laid down in turn, each arm being laid from its outermost portion inward, the lower arm first. The mode of construction of the cruciate device suggests that this type of decoration evolved by duplication and diagonalizing the single two-armed vertical decoration seen in presumptively less derived Argiope. [ABSTRACT FROM AUTHOR]