Spinning activity of the spider Trogloneta granulum (Araneae, Mysmenidae): web, cocoon, cocoon handling behaviour, draglines and attachment discs.

The spider species Trogloneta granulum, which in the wild lives inside scree slopes, builds three-dimensional orb webs. During egg-laying and egg sac building, the females stay with their dorsa down at the central part of the web. In this process, the hub is used as a platform. The threads of the hub are not incorporated into the silk cover of the egg sac. The silk wall of the egg sac is very thin, with all the silken threads constituting it having a uniform ultrastructure. The silk wall of the egg sac and the spinnerets are permanently linked by a dragline. Draglines produced by T. granulum affect the direction of movements of the female carrying its cocoon. Egg sacs are handled using draglines. The low number of piriform glands leads to the formation of very simple attachment discs, which fix the individual threads to the substratum. Thread bundles are attached to the substratum by means of accumulated attachment discs.