FUNCTIONAL-ORGANIZATION OF THE SPINNING APPARATUS OF CYRTOPHORA-CITRICOLA WITH REGARD TO THE EVOLUTION OF THE WEB (ARANEAE, ARANEIDAE)

The spinning apparatus of Cyrtophora citricola closely corresponds to that of orb-weaving Araneidae, two peculiarities excepted. Firstly the spigots of the piriform glands differ extremely in size, the smallest of them being numerous and having a unique location on the anterior s pinnerets. Secondly, the triad complex (on the posterior spinnerets) u sed by other Araneidae for producing gluey capture threads is lacking. Both these characteristics are correlated with the construction of a fine meshed sheet of dry silk by Cyrtophora instead of orbwebs with ca pture spirals. The sheet can be understood as being a very much enlarg ed central area of orb-webs. Since vestiges of triads could be found i n early developmental stages of C. citricola, the origin of the meshed sheet from orb-webs with gluey capture threads is clearly demonstrate d. The paper includes a study on how the spider produces thread attach ments by means of the secretions of the piriform glands.