178 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



an old fashioned spinning wheel, and is apparently used to separate into 

 a flossy mass the threads of silk as they issue from the spinning glands. 

 Bertkau, in an article on the cribellum and calamistrum, has shown cer- 

 tain secreting glands at the ends of the fine tubes which have their 

 outlets in the former organ. It is not improbable, in view of this dis- 



covery, that the viscidity of the flocculent spirals 



of Uloborus and other spiders possessing this 



organ is caused in some measure by a slight 



secretion from these glands. 



It is the possession of cribellum and cala- 



mistrum by Uloborus and Hyptiotes which has 

 led various arachnologists to separate 



Calamis- these two genera from the Orbweavers. 



C ibellum Emerton, for example, following Black- 

 wall, Keyserling, and Bertkau, assigns 



them to the Clubionidse. Without entering at 



FIG. 165. Spinning organs of Clubiona, , , . , , , ,, 



showing the cribeiium, cb. P, pos- length into the reasons, based upon structure, tor 



^^Iffi^^cSSr dissenting from this opinion, I have felt con- 



Biackwaii.) strained, on the grounds of their spinningwork 



alone, to place both these genera among the Orbitelariae, where indeed such 



a distinguished systematic arachnologist as Professor Thorell has already 



placed them, and continues to keep them, notwithstanding all the objec- 



tions that have been advanced by the able naturalists who have espoused 



the other view. 



Mr. Emerton has made some studies of the web of Uloborus Walck- 

 enaerius, the common species of Northern Europe. I reproduce his figure 

 (Fig. 167), which represents an unfinished web of this species 

 geen ^ jr ranca j^ shows the central part still occupied by the 

 preliminary spirals or scaffolding, while the outer part is covered 

 with curled threads, arid the smooth spirals cut away (or not yet inserted), 

 leaving thickened spots or ribbons on the rays. In the finished web most 

 of the spirals pass regularly around, but the outer ones are often more or 

 less irregular, as in Epeira webs, according to the shape of the space in 

 which the web is made. 



According to this author, Uloborus 5 after inclosing her eggs in the co- 

 coon, becomes careless about her web, 

 and repairs it only enough to keep the 

 cocoons in place, so that many imper- 

 fect and irregular webs are found at 

 the cocooning season. The only web 

 of Uloborus plumipes seen by Emerton 

 was imperfect from the above cause, but was evidently the remains of a 

 nearly round web, the rays meeting somewhat nearer the upper than the 

 lower edge. 



European 



FIG. 166. Curled thread of Clubiona. 



(After Staveley.) 



