Maturing and Coordination of Web-Building Activity

Experiments are reported in which 114 Zygiella x-notata Cl.spiderlings were taken out of the cocoon before the time atwhich they normally left (2 weeks after the second molt); 67were placed on wooden frames and 47 on wire frames. Both groupsbuilt partial, irregular thread-patterns at first, and, as theygrew older, constructed more and more regular geometric orb-webs:the transition can be traced through several stages. The shapeof the web, particularly the presence of the free-sector, wasdependent on the frame; webs built in a circular wire framelacked the free-sector. It is assumed that the accomplishmentof full, regular orb webs is essentially based on the progressivehistological differentiation of the central nervous system inthe spiderlings during the developmental phase under observation;the wire frame could influence the shape of the web throughmaking construction of a retreat difficult.