A derivative of the orb web and its evolutionary significance

Abstract

This paper describes a new kind of ladder-web structure in which there are two ladders, one above and one below a centrally positioned orb. It differs from previously described ladder-webs, not only because of the two ladders but also because of its 24 h (or more) duration, its vertical placement against the trunks of trees, and the fact that it apparently offers the spider protection against parasitism. Both the spider (Araneus atrihastulus) and its ladder-web are ideally adapted to the tree-trunk: the web with regard to its position, shape, and lack of visibility; and the spider in respect of its coloration, daytime posture, and proximity to the snare. It is concluded that the design of this web offers a number of advantages which evidently enhance the spider's survival and increase its capture potential over and above that of the simple orb.

Keywords:

• ladder-web
• scentral orb
• adaptation
• protection
• crypticity
• prey-capture potential
• spiders: Araneus