The silk-producing system of Linyphia triangularis (Araneae, Linyphiidae) and some comparisons with Araneidae. Structure, histochemistry and function

The spinning apparatus of Linyphia triangularis, adult females and males, was studied with the scanning electron microscope and the main anatomical and histochemcial characteristics of the silk glands, including the epigastric apparatus of males, are presented. The epigastric glands seem to be important for the construction of sperm webs. A detailed account of the use of the different kinds of silk in web building is given. This spinning apparatus of Linyphia closely corresponds to the araneid pattern. Characteristic of linyphiid spiders is the poor development of the aciniform glands. Corresponding to the minor importance of capture threads of Linyphia, the triads (aggregate and flagelliform glands) are less developed than in Araneidae. Linyphia make much less use of the secretions of the piriform glands for connecting threads than Araneidae. Capture threads adhere to other threads of their own glue; other threads seem mostly to be bound to one another by the secretion of the minor ampullate glands whose chemical properties, in Linyphia, appear espescially adapted to this function. Neither the anatomical and histochemical data concerning the spinning apparatus nor the structure of the webs provide any indication of close relationships between Linyphiidae and Agelenidae, as was recently claimed.