Elongated orb-webs of Australian ladder-web spiders (Araneidae: Telaprocera) and the significance of orb-web elongation

Many orb-web spiders build modified, asymmetrical orbs. Ladder-webs (a general term describing highly elongated orb-webs) are extreme examples of modified orbs built by several spider species in different families. Australian ladder-web spiders, Telaprocera (Araneidae), build highly elongated orbs consisting of a centralised orb-like portion with ladder extensions above and below. Webs are built exclusively on tree trunks, although most of the web is not in direct contact with the tree surface, as in some other ladder-web species. This study provides the first detailed description of the web structure, web-building behaviour and habitat preferences of Telaprocera spiders and discusses possible functions of this highly elongated orb-web form. The ladder-web of Telaprocera is probably an adaptation to building against trees, rather than the proposed moth specialisation function in some other ladder-web species. This has also been suggested for an African ladder-web spider Clitaetra irenae. Additionally, the web-building behaviour of Telaprocera spiders differs from that of the New Zealand ladder-web spider, Cryptaranea atrihastula, despite its remarkably similar web form.